The fall of Moamer Kadhafi's hometown of Sirte will mark an "iconic" moment in Libya but it will not spell the end of NATO's air campaign, the alliance's top military officer told AFP on Tuesday.

Admiral Giampaolo Di Paola, chairman of the NATO military committee, said Kadhafi loyalists were like a "cornered beast" as the new regime forces took control of key positions in the coastal town.

"When the ferocious beast is cornered, she will fight until the end," Di Paola said in an interview at NATO headquarters. "On the one hand, yes, I am surprised by their capacity to resist but, on the other hand, they have no other choice."

The National Transitional Council (NTC) force seized the police headquarters of Sirte on Tuesday, two days after taking control of the town's showpiece conference centre, university campus and main hospital.

Two months after the NTC took control of Tripoli, Kadhafi forces are holding on to only one other bastion, the southern desert town of Bani Walid, where the fighting has caused civilians to flee.

"Every day that passes, the situation in both towns, Sirte and Bani Walid, becomes less and less tenable for the forces that are resisting," said Di Paola, who chairs the committee of military chiefs from NATO's 28 member states.

The Italian admiral said NTC victory in Sirte "will be an iconic moment" but that NATO will only end the mission once civilians are definitely out of harm's way and the NTC is capable of keeping the whole country safe.

"The fall of Sirte is an important element, but like any decision it will not be the only factor," he said.

A NATO diplomat said some allies will want the six-month-old mission to end once Sirte falls but others will argue that the alliance should make sure that all of Libya is secure before terminating the operations.

"It's premature to work on closing the operation," the diplomat said on condition of anonymity.

Despite a dramatic reduction in alliance air strikes in recent weeks, NATO defence ministers vowed after talks last week to keep bombing Kadhafi loyalists as long as civilians are under threat.

The last air strike in Sirte, for instance, took place on October 7 against a military vehicle.

Colonel Roland Lavoie, the operation's military spokesman, said the close-quarter urban combat is restricting NATO missions as the alliance wants to avoid causing civilian casualties.

The refusal of Kadhafi forces to give up in Sirte "could be qualified as surprising," Lavoie told a news briefing.

"The posture of pro-Kadhafi forces at this stage just does not make sense," he said, given that "they could not change or influence the outcome of this conflict."

Di Paola said any decision to end Operation Unified Protector will be taken in concert with the NTC and the United Nations, which provided the mandate for the air war that started in March.

"It think it will end very quickly, but I don't have a crystal ball," he said. "I think it's very close."