Libyan rebel fighters say they have fought their way into the strategic city of Zawiya.

Some rebel fighters have reached the city's central main square, however, they say snipers and troops loyal to Libyan leader Moammar Gadhafi remain in the town.

Zawiya, located 50 kilometers west of Tripoli, lies on the main highway between Tripoli and the border with Tunisia. Rebel control of Zawiya would cut off Tripoli from its supply lines.

On Saturday, rebels said they had seized the town of Gharyan, which is located about 100 kilometers from the capital. Later in the day, the Associated Press quoted an opposition fighter who said a second round of clashes broke out after pro-government forces returned with reinforcements.

In a separate development, a Libyan government official slammed U.N. chief Ban Ki-moon on Saturday for comments that that he made earlier in the week concerning civilian casualties.

On Thursday, Mr. Ban expressed concern about the rising number of civilian deaths and urged all sides to “exercise extreme caution.”

Deputy Foreign Minister Khaled Kaim said that Mr. Ban's remarks were “unacceptable” because they did not single out NATO as being responsible for civilian deaths.

On Tuesday, Libya accused NATO of killing 85 people in a village near the western town of Zlitan. NATO said its warplanes had hit targets in the area the previous day but denied evidence of civilian casualties.

NATO began launching air strikes against in March, supporting rebels who have been fighting against Mr. Gadhafi's 42-year rule.