Fierce clashes have erupted on two fronts between forces loyal to Libyan leader Moammar Gadhafi and rebels who have been trying to advance toward Tripoli.

Rebels initially said on Saturday that 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.

Meanwhile, rebels pushed Saturday toward Zawiya, a city located 50 kilometers west of Tripoli. But, the government has denied the rebels' claim that they captured the city.

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.