Thirteen troops and dozens of Muslim extremists were killed yesterday in clashes between government forces and al-Qaeda-linked rebels on the southern island of Basilan, the military said.
They said fighting broke out in the jungle when Marines launched an attack on a rebel camp, killing as many as 42 members of the Abu Sayyaf extremist group.
Details of the incident remained sketchy amid a media blackout imposed by the military on Basilan, but the sources said the gun battle on the outskirts of the town of Unkaya Pukan turned into close-quarters combat.
"The enemy suffered a lot of casualties. We are still trying to get the exact number but the casualties are heavy," military spokesman Major Eugene Batara said.
"The offensive is continuing," he told reporters in Zamboanga City.
He said two Marines and two Abu Sayyaf commanders were confirmed dead but that there would be more casualties on both sides.
The media blackout on Basilan was imposed amidst a military build-up in response to the death of 14 Marines in a July 10 ambush.
That attack was blamed on the Abu Sayyaf and members of the Moro Islamic Liberation Front, a group which is negotiating peace with the government.
Since then the government has been pouring forces into Basilan for a likely offensive against the extremists.