The three ICRC workers have been held in the jungles of Jolo since January 15.

They were abducted after a visit to a local prison where the ICRC is funding a water project.

Swiss appeal

The Swiss government appealed for the release of the captives on Wednesday.

"We appeal to your sense of humanity. Please spare the lives of the hostages," the Federal Council said in a public statement.

"We implore the kidnappers to show compassion and to release Mary Jean, Andreas and Eugenio without further delay and in good health."

Al Jazeera's Marga Ortigas, reporting from Manila, said there had been no word from the Abu Sayyaf group since the deadline passed at 2pm (0600GMT) on Tuesday.

Our correspondent said there were indications the hostages were being moved deeper into the jungle of Jolo island, suggesting the group was preparing for battle.

Abu Sayyaf has demanded the withdrawal of troops from the island, but the demand has been rejected by the Philippine government.

Military advance

Puno said about 2,000 troops and local security forces had re-established a cordon around the kidnappers and the hostages in the interior jungles of Jolo once the deadline expired.

They had intially withdrawn a few kilometres at the weekend to placate the group.

"Now that we have got back to the positions that we left before, I think that the cordon is in place and we will just wait to see what the developments are from now on," Puno said.

About 2,000 troops staged a cordon around the kidnappers on Jolo island [AFP]
 
Security officials said a last-ditch attempt by two politicians on Jolo to negotiate the release of the hostages failed on Tuesday after Sakur Tan, the governor of Jolo, declared a state of emergency in the province.

The state of emergency included a curfew, roadblocks and the redeployment of the government forces near the Abu Sayyaf camp.

Richard Gordon, the head of the Philippines ICRC, said on Wednesday that he wanted proof from the Abu Sayyaf that the hostages were unharmed.

"I want to talk to the three. It is a measure to rebuild confidence," he said in a radio interview.

Other officials said intermediaries had established contact with the kidnappers, but no details have been made immediately available.

The Abu Sayyaf group, which has been linked to the regional Jemaah Islamiyyah and to al-Qaeda, has been blamed for the worst attack in the Philippines' history, in which a ferry in Manila Bay was bombed in 2004, killing 100 people.