The Philippine government and a Muslim rebel group have been urged to end a three-day battle that has left at least 12 people dead and displaced thousands.
The Organisation of the Islamic Conference (OIC) called on both sides to abide by a 1996 peace agreement.
Government troops and helicopter gunships pounded a base of the Moro National Liberation Front (MNLF) on southern Jolo island at the weekend.
It followed a mortar attack on two marine camps on Friday.
That attack, which killed two marines and a child, has been blamed on an MNLF commander, Habier Malik.
Government forces retaliated by deploying as many as 3,000 troops and dropping bombs and rockets on to Habier Malik's base near the town of Panamao.
Army officials said at least nine rebels had been killed as the hunt for Malik and his followers continued.
More than 8,000 villagers had fled their homes to avoid the gunfire and were being sheltered in Jolo town, officials said.
The secretary-general of the OIC, which is the world's largest grouping of Muslim countries, called for an "immediate cessation of the military operations" on Jolo.
Professor Ekmeleddin Ihsanoglu urged both sides to abide by a peace deal they signed in 1996 and "to resume negotiation in good faith for the full implementation of that agreement".
Jesus Dureza, the government's adviser on peace talks with rebels, said he wanted the armed forces to finish their offensive as soon as possible.
And he stressed the government was going after Malik, not MNLF.
"The military operation is not against the MNLF organisation," Mr Dureza said.
"It is a limited military action against an MNLF rogue commander who staged an unprovoked attack on Panamao resulting in the death and injuries of civilians and damage to properties."
Some news reports quoted Malik as saying he was avenging an incursion into an MNLF stronghold by troops hunting fighters from the Abu Sayyaf Muslim rebel group last week.
Another report suggested he may be pressuring the government to release jailed MNLF founder Nur Misuari.
The island of Jolo is some 950km (600 miles) south of the Philippine capital, Manila.