TRIPOLI, Libya: Diehards of slain Libyan dictator Moamer Gadhafi attacked a base in his one-time bastion of Bani Walid killing at least four ex-rebel fighters and wounding 20 others Monday, a local official told AFP.

"There are at least four martyrs from the thuwar (anti-Gadhafi revolutionaries) and 20 are injured," said Mahmud Warfelli, spokesman of Bani Walid local council, in the attack -- the first major outburst of violence in the town since the end of the anti-Gadhafi conflict in October.

He said the attack was launched by "a group of remnants of the old regime," and called for outside help against a feared "massacre."

"There are around 100 and 150 men armed with heavy weapons who are attacking. We have asked for the army to intervene, but the defense ministry and NTC (National Transitional Council) have let us down," he said.

"We're out of the frying pan into the fire. We've been warning about this for the past two months," he said.

Another local official, M'barek al-Fotmani, said the assailants had circled the base of former rebels who helped topple Gadhafi last year.

"The compound of thuwar is surrounded on all sides by loyalists of Gadhafi who are attacking it with all kinds of weapons," said Fotmani, a former NTC member for Bani Walid, 170 kilometers (110 miles) southwest of Tripoli.

"The attackers are carrying green flags," symbol of the Gadhafi regime, he said from inside the base.

Fotmani said the base belonged to the May 28 Brigade, a unit of former rebels attached to the defense ministry.

"The attackers shouted 'Allah, Moamer, Libya and that's it!," he said, referring to a slogan popularized by Gadhafi loyalists during his rule.

"Yesterday they had distributed leaflets saying "We will be back soon. We will take the rats out,'" Fotmani added.

"I call upon Libya to save Bani Walid thuwar urgently. Their ammunition is almost over."

He also said ambulances were unable to evacuate those wounded because there were "snipers positioned on a school and a mosque in the vicinity" of the attack.

Bani Walid was one of the last pro-Gadhafi bastions to fall in the bloody uprising against the former dictator's rule.

The capture of Bani Walid was followed by the fall of the longtime strongman's hometown Sirte in a battle which also led to his killing and marked the "liberation" of Libya.