BBC
Opposition activists have called on protesters to march on the site of the now-demolished Pearl Roundabout - the focus of last year's unrest.
A BBC correspondent says the area is quiet, but that in outlying villages there have been violent clashes.
Police have been firing rubber bullets and tear gas at stone-throwing youths.
Most of the demonstrators are from the Gulf kingdom's Shia Muslim majority, which has long complained of discrimination at the hands of the Sunni royal family, the Al Khalifa, and wants democratic reforms.
Roads blocked
The BBC's Bill Law, who is in Manama, says the centre of the capital remains quiet, with no sign of the mass protest called by the opposition a year on from the peaceful takeover of Pearl Roundabout.
Opposition activists had called for people to converge on the area at 0630 (0330 GMT).
There is a massive police and army presence in the city, and roads to and from Shia villages on the outskirts have been closed, our correspondent adds.
However, a number of protesters are attempting to march towards the capital from the villages of Sanabis, al-Daih and Jidhafs, which lie a few kilometres to the west, witnesses told the AFP news agency.
Overnight, riot police used tear gas and stun grenades to disperse demonstrations in several villages, including Sitra and Sanabis. Some protesters threw stones and Molotov cocktails.
On Tuesday morning, the government issued a statement blaming the main Shia opposition party, al-Wefaq, for turning what it said should have been a peaceful, government-sanctioned demonstration in the capital into a riot.
Protesters reportedly managed to get within 2km (1.5 miles) of the former site of Pearl Roundabout before being pushed back by riot police.
Khalil al-Marzuq of al-Wefaq said the opposition was willing to engage in dialogue with King Hamad Bin Isa al-Khalifa's government, but that ministers were interested only in showing the international community that they were "taking some steps" towards democratic reform.
He also urged protesters not to resort to violence.
"Your strength is in being peaceful... continue to be peaceful," he said. "Don't retaliate. Don't confront the riot police even if they attack you because you will win at the end," he told the BBC.
"This is a non-violent movement and should continue to be non-violent, because your cause is justice and you will get at the end what you want."
'Excessive force'
At least 35 people were killed between February and March 2011, 30 of them civilians and five security forces personnel, according to the human rights commission. It also found that security forces had used excessive force and tortured detainees, including five who died.
Last month, King Hamad tried to address some of the protesters' demands by announcing constitutional reforms intended to lead to greater accountability.
He also ordered the rebuilding of Shia mosques and the reinstatement of those who had lost their jobs, and appointed two British lawyers to overhaul the judicial system.
But the opposition, as well as human rights groups, say that the violent crackdown on dissent is continuing.
On Monday, Hassiba Hadj Sahraoui, of Amnesty International's Middle East and North Africa programme, said: "The government has made a number of announcements of what it has done to improve the human rights situation, but the fact is that it has still not delivered in the most important areas."
Demonstrators advanced about 2km (1.5 miles) on Pearl Roundabout before they were pushed back
A heavy police presence is preventing people marking the first anniversary of pro-democracy demonstrations in Bahrain's capital, Manama.
A BBC correspondent says the area is quiet, but that in outlying villages there have been violent clashes.
Police have been firing rubber bullets and tear gas at stone-throwing youths.
Most of the demonstrators are from the Gulf kingdom's Shia Muslim majority, which has long complained of discrimination at the hands of the Sunni royal family, the Al Khalifa, and wants democratic reforms.
Roads blocked
The BBC's Bill Law, who is in Manama, says the centre of the capital remains quiet, with no sign of the mass protest called by the opposition a year on from the peaceful takeover of Pearl Roundabout.
Opposition activists had called for people to converge on the area at 0630 (0330 GMT).
Continue reading the main story 
The situation right now is that downtown Manama is quiet, almost eerily quiet, a year on from the peaceful takeover of Pearl Roundabout. There is a very heavy police presence, with personnel stationed on the corners of major roads. Many roads leading to the capital were also blocked. A few people have made their way to Pearl Roundabout, but any kind of mass demonstration there has not yet materialised.
However, there have been many disturbances in predominantly Shia villages on the outskirts of the capital. Police are firing rubber bullets, tear gas and stun grenades at demonstrators, who are throwing stones. There was very heavy use of tear gas in Sanabis overnight, and a resident of Sitra said the streets outside his house were littered with spent tear-gas canisters.
The government, which is dominated by the Sunni royal family, says it is meeting its commitments to introduce political reforms and curb the police. But the mostly Shia opposition says the government is not doing enough.
At the scene
However, there have been many disturbances in predominantly Shia villages on the outskirts of the capital. Police are firing rubber bullets, tear gas and stun grenades at demonstrators, who are throwing stones. There was very heavy use of tear gas in Sanabis overnight, and a resident of Sitra said the streets outside his house were littered with spent tear-gas canisters.
The government, which is dominated by the Sunni royal family, says it is meeting its commitments to introduce political reforms and curb the police. But the mostly Shia opposition says the government is not doing enough.
The roundabout, and the Pearl Monument that used to stand in the centre of it, were demolished and replaced by a new road junction last March, after protesters were forced out violently by the authorities.
However, a number of protesters are attempting to march towards the capital from the villages of Sanabis, al-Daih and Jidhafs, which lie a few kilometres to the west, witnesses told the AFP news agency.
Overnight, riot police used tear gas and stun grenades to disperse demonstrations in several villages, including Sitra and Sanabis. Some protesters threw stones and Molotov cocktails.
On Tuesday morning, the government issued a statement blaming the main Shia opposition party, al-Wefaq, for turning what it said should have been a peaceful, government-sanctioned demonstration in the capital into a riot.
Protesters reportedly managed to get within 2km (1.5 miles) of the former site of Pearl Roundabout before being pushed back by riot police.
Khalil al-Marzuq of al-Wefaq said the opposition was willing to engage in dialogue with King Hamad Bin Isa al-Khalifa's government, but that ministers were interested only in showing the international community that they were "taking some steps" towards democratic reform.
He also urged protesters not to resort to violence.
"Your strength is in being peaceful... continue to be peaceful," he said. "Don't retaliate. Don't confront the riot police even if they attack you because you will win at the end," he told the BBC.
"This is a non-violent movement and should continue to be non-violent, because your cause is justice and you will get at the end what you want."
'Excessive force'
At least 35 people were killed between February and March 2011, 30 of them civilians and five security forces personnel, according to the human rights commission. It also found that security forces had used excessive force and tortured detainees, including five who died.
Continue reading the main story
“Start Quote
Hassiba Hadj Sahraoui Amnesty InternationalThe government has made a number of announcements of what it has done to improve the human rights situation, but the fact is that it has still not delivered in the most important areas”
Almost 3,000 people were also arrested by security services after a state of emergency was declared by King Hamad in March. Scores were tried by military courts and sentenced to prison terms of up to life after what human rights activists said were grossly unfair trials.
More than 4,000 private sector employees and civil servants were also dismissed from their jobs, and at least 30 Shia prayer centres were demolished.Last month, King Hamad tried to address some of the protesters' demands by announcing constitutional reforms intended to lead to greater accountability.
He also ordered the rebuilding of Shia mosques and the reinstatement of those who had lost their jobs, and appointed two British lawyers to overhaul the judicial system.
But the opposition, as well as human rights groups, say that the violent crackdown on dissent is continuing.
On Monday, Hassiba Hadj Sahraoui, of Amnesty International's Middle East and North Africa programme, said: "The government has made a number of announcements of what it has done to improve the human rights situation, but the fact is that it has still not delivered in the most important areas."
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