BBC
Ministers will consider responses to a report by the UN nuclear watchdog that said Iran had carried out tests related to "development of a nuclear device".
Iran denies this, saying its nuclear programme is for peaceful purposes.
Britain may press for further sanctions against Iran's energy sector, reports say, after the storming of British diplomatic compounds in Tehran.
On Wednesday, the UK announced that it was expelling all Iranian diplomats and closing the Iranian embassy in London after the attacks of the previous day.
The British Foreign Secretary William Hague also announced that all UK diplomatic staff in Tehran had been evacuated and the embassy closed.
BBC Iran correspondent James Reynolds, in Brussels where the talks are taking place, says the meeting is a first chance to see if other countries in Europe will follow Britain in taking their own measures against Iran.
Already France, Germany and the Netherlands have recalled their respective ambassadors from Tehran for consultations.
Iran will be watching closely, our correspondent says.
Its foreign ministry has criticised the decision to close the embassies in London and Tehran as a hasty knee-jerk reaction, but some hardliners have welcomed the move.
One Islamic students' society says it will hold thanksgiving services to celebrate the embassies' closure.
Stern warning
But the attack could go some way towards convincing EU countries that stronger action against Iran is needed, reports quoting diplomatic officials say.
France will push the foreign ministers to look at sanctions beyond what had already been agreed, especially proposals by President Nicolas Sarkozy to freeze the Iranian central bank's assets and to ban oil imports, French Foreign Ministry spokesman Bernard Valero was quoted by Reuters as saying.
But there are fears that a European oil embargo could raise global crude oil prices at a time when Europe is threatened by recession and struggling with a mounting debt crisis.
In addition to discussing sanctions, EU governments are reportedly considering a stern warning to Tehran over the attack on Britain's interests.
France, Germany and the Netherlands have already recalled their ambassadors from Tehran for consultations.
Norway said it was temporarily closing its embassy there as a precaution, and Italian Foreign Minister Giulio Terzi said the Iranian ambassador to Rome was being summoned to give guarantees of security for Italy's mission in Tehran.
The BBC's diplomatic correspondent Jonathan Marcus says Western leaders insist that sanctions on Iran essentially have two purposes.
One is to constrain Iran's nuclear activities by restricting the country's access to advanced tooling, crucial materials and so on.
Second, by applying pressure to individuals and key sectors of the economy, the hope is to persuade the Iranians back to the negotiating table.
But our correspondent says all the indications are that this approach is only partially working.
Lowest level
On Wednesday, Mr Hague told parliament he was demanding the immediate closure of the Iranian embassy in London, with all its staff to leave the UK within 48 hours.
"If any country makes it impossible for us to operate on their soil they cannot expect to have a functioning embassy here," Mr Hague told MPs.
He said there had been "some degree of regime consent" in the attacks on the British embassy and on another UK diplomatic compound in Tehran.
Iran's foreign ministry called the British move "hasty", state TV reported, and said Iran would take "further appropriate action".
Hundreds of protesters - whom Iran described as "students" - massed outside the embassy compound on Tuesday afternoon before scaling the walls and the gates, burning British flags and a car.
Another UK diplomatic compound in northern Tehran, known locally as Qolhak Garden, was also overrun and damaged.
Iran said it regretted the incident, which it described as "unacceptable behaviour by a small number of protesters".
The US, EU and UN Security Council also condemned the attacks.
Turbulent history 
Wednesday's move brought bilateral relations to their lowest level since 1989 when ties were broken over Iran's declaration of a "fatwa" (edict) to kill the author Salman Rushdie.
Last week the US, Canada and the UK announced new sanctions against Iran, including measures to restrict the activities of the Iranian central bank.
The UK said then it was severing all financial ties with Iran.
On Sunday, Iran's parliament voted by a large majority to downgrade diplomatic relations with the UK in response to the recent action.
Mr Hague said there had been a "degree of regime consent" in the British embassy attack
Discussion of new measures against Iran is expected to dominate a meeting of European foreign ministers on Thursday.
Iran denies this, saying its nuclear programme is for peaceful purposes.
Britain may press for further sanctions against Iran's energy sector, reports say, after the storming of British diplomatic compounds in Tehran.
On Wednesday, the UK announced that it was expelling all Iranian diplomats and closing the Iranian embassy in London after the attacks of the previous day.
The British Foreign Secretary William Hague also announced that all UK diplomatic staff in Tehran had been evacuated and the embassy closed.
BBC Iran correspondent James Reynolds, in Brussels where the talks are taking place, says the meeting is a first chance to see if other countries in Europe will follow Britain in taking their own measures against Iran.
Already France, Germany and the Netherlands have recalled their respective ambassadors from Tehran for consultations.
Iran will be watching closely, our correspondent says.
Its foreign ministry has criticised the decision to close the embassies in London and Tehran as a hasty knee-jerk reaction, but some hardliners have welcomed the move.
One Islamic students' society says it will hold thanksgiving services to celebrate the embassies' closure.
Stern warning
Continue reading the main story 
Britain, encouraged by the outspoken support of countries like China as well as Europe and the United States, has decided to make the toughest response possible to Tuesday's attacks on the British embassy buildings in Tehran.
Most of the countries that have been supportive - including France, Germany, Austria and Turkey - have become increasingly worried about the erratic way that Iran has been behaving, and worried too about its aims and intentions now that it seems close to being able to assemble a nuclear weapon.
It seems certain that the extreme conservatives, who nowadays look to the Supreme Leader, Ali Khamenei, were behind the attack on the British embassy.
Their aim was to discredit President Ahmadinejad, who despite his own radicalism can see advantages in keeping up relations with the West.
Analysis
Most of the countries that have been supportive - including France, Germany, Austria and Turkey - have become increasingly worried about the erratic way that Iran has been behaving, and worried too about its aims and intentions now that it seems close to being able to assemble a nuclear weapon.
It seems certain that the extreme conservatives, who nowadays look to the Supreme Leader, Ali Khamenei, were behind the attack on the British embassy.
Their aim was to discredit President Ahmadinejad, who despite his own radicalism can see advantages in keeping up relations with the West.
Tuesday's storming of the UK embassy on Tehran by hundreds of protesters followed Britain's decision to impose further sanctions on Iran over its nuclear programme.
France will push the foreign ministers to look at sanctions beyond what had already been agreed, especially proposals by President Nicolas Sarkozy to freeze the Iranian central bank's assets and to ban oil imports, French Foreign Ministry spokesman Bernard Valero was quoted by Reuters as saying.
But there are fears that a European oil embargo could raise global crude oil prices at a time when Europe is threatened by recession and struggling with a mounting debt crisis.
In addition to discussing sanctions, EU governments are reportedly considering a stern warning to Tehran over the attack on Britain's interests.
France, Germany and the Netherlands have already recalled their ambassadors from Tehran for consultations.
Norway said it was temporarily closing its embassy there as a precaution, and Italian Foreign Minister Giulio Terzi said the Iranian ambassador to Rome was being summoned to give guarantees of security for Italy's mission in Tehran.
Foreign Secretary William Hague: "We require the immediate closure of the Iranian embassy in London"
One is to constrain Iran's nuclear activities by restricting the country's access to advanced tooling, crucial materials and so on.
Second, by applying pressure to individuals and key sectors of the economy, the hope is to persuade the Iranians back to the negotiating table.
But our correspondent says all the indications are that this approach is only partially working.
Lowest level
On Wednesday, Mr Hague told parliament he was demanding the immediate closure of the Iranian embassy in London, with all its staff to leave the UK within 48 hours.
"If any country makes it impossible for us to operate on their soil they cannot expect to have a functioning embassy here," Mr Hague told MPs.
He said there had been "some degree of regime consent" in the attacks on the British embassy and on another UK diplomatic compound in Tehran.
Iran's foreign ministry called the British move "hasty", state TV reported, and said Iran would take "further appropriate action".
Hundreds of protesters - whom Iran described as "students" - massed outside the embassy compound on Tuesday afternoon before scaling the walls and the gates, burning British flags and a car.
Another UK diplomatic compound in northern Tehran, known locally as Qolhak Garden, was also overrun and damaged.
Iran said it regretted the incident, which it described as "unacceptable behaviour by a small number of protesters".
The US, EU and UN Security Council also condemned the attacks.
Turbulent history
Iranian protesters searched offices at the British embassy
Relations between the UK and the Islamic Republic of Iran have been fraught since the Iranian revolution in 1979.Wednesday's move brought bilateral relations to their lowest level since 1989 when ties were broken over Iran's declaration of a "fatwa" (edict) to kill the author Salman Rushdie.
Last week the US, Canada and the UK announced new sanctions against Iran, including measures to restrict the activities of the Iranian central bank.
The UK said then it was severing all financial ties with Iran.
On Sunday, Iran's parliament voted by a large majority to downgrade diplomatic relations with the UK in response to the recent action.
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