Libya's provisional government says Moammar Gadhafi's son Mutassim has been arrested in the coastal city of Sirte.

National Transitional Council officials Wednesday said Mutassim Gadhafi was taken to the eastern town of Benghazi where authorities questioned him. They gave no additional details.

Earlier, anti-Gadhafi fighters said they now control more than 80 percent of Sirte, Mr. Gadhafi's hometown. However, the fighters said they are still facing stiff resistance from Gadhafi loyalists who hold pockets of the coastal town.

NTC forces have made significant advances in Sirte in recent days. They seized the town's police headquarters on Tuesday.

Days earlier, the fighters gained control of the main hospital, the university and the convention center that Gadhafi loyalists had used as their main base of operation.

NTC officials have said the capture of Sirte will allow them to declare the country liberated, because it will mean the provisional government controls all of Libya's ports and harbors.

NATO said Tuesday it has no evidence of any significant pro-Gadhafi activities in Libya outside of Sirte and the desert town of Bani Walid.

Sirte is 360 kilometers east of Libya's capital, Tripoli, and has served as a center of support for Mr. Gadhafi. Anti-Gadhafi fighters have been trying to move into the town for three weeks.

Pro-Gadhafi forces also are putting up strong resistance in Bani Walid. NTC fighters retreated from the town center after facing heavy sniper fire and booby-traps, but they still hold the airport and two nearby villages.