ZAMBOANGA, Philippines -- Philippine troops gained control of most of a Muslim rebel stronghold in fierce fighting Friday, officials said, but they failed to find the 27 hostages, mostly children, held there for nearly six weeks.
Soldiers found shallow graves believed to contain the bodies of about 20 Abu Sayyaf rebels and suspected other bodies were hidden in the camp's network of foxholes, bunkers and tunnels, Deputy Chief of Staff Jose Calimlim said."When you get near caves and tunnels the smell of dead bodies is overpowering," he said. "We hope this is not of the hostages."
The hostages were among about 50 people seized by the extremist rebels from two schools on March 20. The rebels later released some of the hostages and said they beheaded two last week as a "birthday present" for President Joseph Estrada.
Officials said 80 percent of the rebel base, located on the southern island of Basilan, was under the control of government troops. Defense Secretary Orlando Mercado said the rebels may have hid the hostages in bunkers or tunnels in the heavily forested hillside stronghold.
Troops are cautiously approaching the remaining bunkers, he said.
About 30 rebels were seen retreating toward a hill to the north, some dragging dead or wounded comrades, Mercado said. The area already has been surrounded by troops and government militia, he said.
One soldier was killed and seven wounded in Friday's fighting, bringing the government toll to six dead and 32 wounded since about 1,500 government troops launched the rescue operation last Saturday, officials said.
Estrada warned Friday that the Abu Sayyaf, a Muslim extremist group accused of past kidnappings, would be "pulverized into ashes."
"We will not allow their atrocities to continue," he said.
Meanwhile, a Muslim religious leader acting as a go-between met Friday with an envoy from Muslim extremists holding 21 other hostages, including 10 tourists, snatched Sunday from a Malaysian resort island.
About 500 military and police were deployed around a mountain near the town of Talipao in Sulu, an island about 50 miles southwest of Basilan, where the 21 hostages are thought to be held.
While both kidnappings -- the worst in the Philippines in years -- have been blamed on the Abu Sayyaf, they may not be directly related, since parts of the group are only loosely connected, officials say.
Prospects for negotiations were unclear after an Abu Sayyaf commander holding some of the tourists, Galib Andang, told a local radio station that they would negotiate only with ambassadors from the hostages' countries.
He allowed one of the hostages, Carel Strydom from South Africa, to be interviewed by the radio station, DXRZ. In comments dictated by someone whispering next to him, Strydom said they were all in good health and asked the United Nations to tell the Philippine government to stop its military actions against the rebels.
In a separate radio interview, Abu Ahmad, spokesman of the Basilan rebels, warned that the tourists held in Sulu would be beheaded if their ambassadors refuse to negotiate. But it was not clear how much say Abu Ahmad's group has in the second kidnapping, and Andang did not make a similar threat.
The 21 hostages in Sulu -- including tourists from Germany, France, South Africa, Finland, Lebanon and resort workers from the Philippines and Malaysia -- were snatched by armed men who invaded the Malaysian resort of Sipadan on Sunday.
Nur Misuari, a former rebel leader appointed by Estrada to negotiate, called Friday's meeting between the unidentified religious leader and the representative from the Sulu kidnappers Friday "a major step" and said he expects the kidnapers to present their written demands to him Saturday. If they are unreasonable, he said he would quit the negotiations.
Estrada has ruled out any ransom payment for the hostages. A police official said the kidnappers are demanding $2.4 million and the release of relatives jailed in Malaysia for various crimes.
Defense Secretary Mercado said the military will not halt the offensive in Basilan.
"It's almost over. We will complete it," he told The Associated Press.
The rebels under siege in Basilan have demanded the release of three terrorists from U.S. jails, including Ramzi Yousef, mastermind of the 1993 bombing of the World Trade Center.
In a statement Friday, the U.S. Embassy in Manila said it was deeply concerned about the two kidnappings, and reiterated its refusal to accept the abductors' demands.
"We and the Philippine government have rejected (the Abu Sayyaf's) demands for the release of convicted terrorists imprisoned in the U.S.," the embassy said in a statement. "The United States does not concede to threats or demands made by terrorists."
Abu Sayyaf is one of two Muslim separatist groups battling government troops in the southern Philippines.