Zamboanga City, Philippines  - Philippine police on Monday filed criminal complaints against seven people, including three police officers, for allegedly providing support to Muslim militants holding captive two European Red Cross workers.

The suspects, who also included two village captains and two civilians, were among dozens of people rounded up last week on Jolo island, 1,000 kilometres south of Manila, on suspicion of being supporters of al-Qaeda-linked Abu Sayyaf rebels.

The seven were flown to nearby Zamboanga City over the weekend to face criminal complaints of kidnapping for ransom and illegal detention, said police spokesman Superintendent Jose Bayani Gucela.

"These people acted as conspirators by providing information and logistical support to the Abu Sayyaf," he said. "These are the people who gave the group information about the target."

Gucela said the seven suspects, who were being detained at a regional police headquarters in Zamboanga City, have denied the charges, but he noted that most of them were relatives of Abu Sayyaf rebels involved in the hostage crisis.

The Red Cross workers - Swiss Andreas Notter and Italian Eugenio Vagni - were abducted January 15 along with a Filipino colleague after visiting the provincial jail on Jolo to oversee a water and sanitation project.

Abu Sayyaf rebels freed Mary Jean Lacaba Thursday after 78 days in captivity. Authorities said no ransom was paid for Lacaba's release.

But the kidnappers threatened to kill the remaining hostages if government forces do not withdraw from a large area of Jolo.

Authorities have rejected the demand but stressed that they were willing to negotiate a compromise to ensure that none of the hostages were harmed.

"We cannot in conscience afford to provide the bandits a safe haven for future incidents of kidnapping and piracy," said Lieutenant Colonel Edgard Arevalo, a military spokesman on the hostage crisis.

But he added that a crisis committee led by Governor Abdusakur Tan was pursing "every possible means within the four corners of the law and statute to recover the victims safely."

Arevalo said government forces were keeping the pressure on the kidnappers while "avoiding precipitate actions" that could jeopardize the hostage's safety.

Abu Sayyaf rebels have been blamed for some of the worst terrorist attacks and high-profile kidnappings in the Philippines. They have beheaded hostages, including an American tourist abducted in 2001, when authorities failed to meet their demands. (dpa)