TRIPOLI, Libya — Suspected Moammar Gadhafi's loyalists staged twin attacks on a key oil refinery Monday in possibly coordinated strikes that suggest revolutionary forces still face resistance in areas under their control. At least 15 attackers were killed, an anti-Gadhafi commander said.

The back-to-back assaults in the coastal oil facility at Ras Lanuf — saboteurs setting fires and then a convoy of gunmen riding in from the desert — was a reminder that opposition forces have potential security challenges across Libya despite pushing out Gadhafi's regime from all but a few strongholds.

Col. Hamid al-Hasi, the commander for anti-Gadhafi force in eastern Libya, said a group of 15 employees set fire to the facility, located about 380 miles (615 kilometers) southeast of Tripoli. He said five of the saboteurs were killed and the rest arrested.

In a separate attack, the port was targeted by a convoy of armed men apparently based in a refugee camp about 18 miles (30 kilometers) south of Ras Lanuf. One revolutionary commander, Fadl-Allah Haroun, said a total of 15 people were killed in both attacks.

The size of the ground assault force was unclear, but Haroun said it may have been as big as 40 vehicles.

Former rebels, meanwhile, have been facing stiff resistance from Gadhafi supporters in Bani Walid since last week and have captured most of the northern half of the town, which is one of several remaining bastions of Gadhafi's rule.

Dozens of cars loaded with Libyan families and personal belongings streamed out of the town, about 90 miles (140 kilometers) southeast of Tripoli, in anticipation of a fresh assault.

"The fighting will be very bad," said Fadila Salim as she drove out of Bani Walid. Her son, Mohammed Ibrahim, said there is no electricity, no water and shops are running out of food. He says many are "stuck in their houses and afraid to leave."

NATO warplanes maintained attacks on remaining pro-Gadhafi sites. The military alliance said its targets Sunday focused on Gadhafi's hometown of Sirte, including a military logistics facility and three surface-to-air missile systems.