Tensions are high in Jolo as the fighting continues

Troops are said to have taken over a rebel hideout, but are still facing stiff resistance in some areas.

"There's still heavy fighting in the mountains of Panamao," said Lieutenant-General Alberto Braganza.

The clashes began on Monday, when rebels attacked troops in retaliation for a recent army assault.

Most of the rebels are from the Abu Sayyaf - an al-Qaeda linked organisation - but the group is also thought to include some disgruntled members of the Moro National Liberation Front (MNLF), which signed a peace deal with the government in 1996.

These rebels are loyal to separatist leader Nur Misuari, who used to lead the MNLF until he was jailed on charges of rebellion in 2001.

Guide to Philippine conflict

According to military reports, more than 60 people have now been killed in the past four days, in some of the most intense fighting in the region for years.

Thousands of residents close to the fighting have left their homes, and local Muslim leaders have called for a ceasefire. Extra troops are being deployed in the region, and the government has also sent Abdurahman Jamasali, a former member of the MNLF, to talk to the militants to try to stop the fighting.

But sporadic attacks have prevented him from entering the rebel area.

The latest skirmishes have been concentrated in several towns around Jolo, a known stronghold for Islamic militants.