ARAKAN INDOBHASA

Tripoli, Libya (CNN) -- Libyan opposition fighters continued their march west Monday with a key target in their sights: Sirte, Moammar Gadhafi's birthplace.

Taking the city would be a symbolic victory for the rebels, who regained control of several significant towns over the weekend as coalition airstrikes continued in the North African nation.

Rebel forces claimed to control Ras Lanuf on Sunday. The opposition also appeared to have taken control of the key oil town of al-Brega.

Victories in those cities marked a comeback for the ragtag group of amateur soldiers who are unified by one mission: toppling Gadhafi's nearly 42-year rule.

Rebels said the fight to take over Sirte could be their toughest and bloodiest battle yet.

They credited coalition airstrikes with helping them regain ground, noting that they had encountered little resistance as they headed westward over the weekend.

Coalition officials have said the airstrikes are aimed at enforcing a no-fly zone and protecting civilians.

But Libyan government officials have countered that claim, arguing that coalition forces only target troops loyal to Gadhafi.

"The rebels are making their advance and no one is stopping them. And no one is even talking to them or saying, 'Where are you going?' or 'Why are you taking offensive positions and attacking the Libyan army and Libyan cities?'" Moussa Ibrahim, a Libyan government spokesman, told reporters in Tripoli.

He accused NATO of "starving the Libyan population to get Libya on its knees to beg for mercy."

"They are trying to weaken our spirits. They are not trying to protect civilians," he said.

NATO, which has 28 member countries, formally approved plans Sunday to take control of enforcing a resolution approved by the UN Security Council on March 17. The resolution called for the protection of Libyan civilians as Gadhafi attacked the opposition, and the enforcement of a no-fly zone over the country.

The coalition enforcing the resolution has been led by the United States, the United Kingdom and France.

NATO officials said the handover of enforcing the no-fly zone from the United States and allies should be complete by Monday.

But it could take until Thursday or Friday for the organization to take over the entire mission. NATO officials described the transition as a phased and seamless operation.

"Our mandate is very clear. We're there to protect civilians against attacks. No more, no less," NATO Secretary General Anders Fogh Rasmussen told CNN.

Rasmussen said military commanders will make decisions on day-to-day operations within the framework NATO members agreed upon over the weekend. He declined to discuss specific rules of engagement, but stressed that NATO was also enforcing an arms embargo in Libya.

"We are not in Libya to arm people, but to protect people," he said.

Meanwhile, President Barack Obama is scheduled to deliver a speech about the situation in Libya at 7:30 p.m. ET Monday following calls from all quarters for the U.S. leader to clarify why he sent troops to enforce the U.N.-authorized military mission.

On Monday, Libyan state television displayed images of injured people in a hospital and destroyed buildings as it reported that civilians were wounded when bombs struck the central Libyan city of Sabha in the early morning hours. CNN was unable to independently verify that report.

U.S. Defense Secretary Robert Gates on Sunday accused Gadhafi of placing the bodies of people his regime has killed at the sites of some missile strikes by the U.S.-led coalition.

"The truth of the matter is we have trouble coming up with proof of any civilian casualties that we have been responsible for," Gates told "Face the Nation" on CBS.

"But we do have a lot of intelligence reporting about Gadhafi taking the bodies of the people he's killed and putting them at the sites where we've attacked."

While the opposition rolled westward, the city of Misrata -- between the rebels' current position and Tripoli -- remained under siege by government forces for the 11th consecutive day, a witness told CNN Sunday.

A doctor working at a hospital in Misrata said eight civilians were killed and 22 injured in violence Sunday. CNN could not independently confirm his report.

French warplanes on Sunday led airstrikes on armored vehicles and on a large munitions depot in the regions of Misrata and Zintan, according to the French Ministry of Defense.

http://edition.cnn.com/2011/WORLD/africa/03/28/libya.war/index.html?hpt=T1