The Philippines military has agreed to pull back its forces from pursuing the kidnappers of three Red Cross workers, in return for the release of one of the hostages, a military spokesman has said.

The three aid workers were kidnapped more than two months age and are believed to be held hostage by fighters from Abu Sayyaf – a Muslim separatist group that intelligence agencies say has ties to al-Qaeda.

The military announcement came after an Abu Sayyaf commander threatened to behead the hostages if government forces launched a new attack on his group.

"We will reposition our troops as necessary to allow the exhaustion of other peaceful means for the safe release of the victims," Lt. Col. Ernesto Torre, a Philippine military spokesman, said in a statement on Thursday.

He said the safety of the International Committee of the three aid workers - Swiss Andreas Notter, Filipino Mary Jean Lacaba and Italian Eugenio Vagni - was the government's "paramount concern".

Earlier this week a series of intense clashes broke out on the southern island of Jolo between soldiers and fighters thought to be holding the hostages.

The fighting left at least three soldiers and three fighters dead.

Military officials said they later found a tent belonging to the three aid workers.

On Wednesday a man claiming to Abu Sayyaf commander Albader Parad telephoned a Philippine TV station to say the three Red Cross hostages were alive, but that their safety was at risk if government forces kept up their offensive.