ZAMBOANGA CITY, Philippines (AP) _ Government forces surrounded Moslem guerrillas who reportedly took 300 families hostage in a coastal town on southern Mindanao island, a regional commander said today.

Maj. Gen. Cesar Tapia said he told his troops to continue trying to flush out about 300 guerrillas of the Moro National Liberation Front holed up in the village of Pangarunan. However, he told them not to mount a direct assault.

''Our primordial concern is the lives of the civilians,'' Tapia told reporters after visiting Sibuco near where government and rebel forces have been fighting since Monday. Sibuco is 30 miles north of Zamboanga City and 500 miles southeast of Manila.

About 500 guerrillas had occupied five villages around Sibuco, Tapia said. But they were driven out from at least three villages in fighting that left seven rebels dead. Two militiamen were killed and six others wounded, he said.

He said the main rebel band, made up of about 300 fighters under commander Asbirin Kalahuddin, reportedly regrouped in Pangarunan and took the residents hostage. They were surrounded by two Filipino marine battalions on land and five navy gunboats offshore.

Earlier, officials of the Southern Command said 500 rebels were holding the hostages.

Tapia said officials in Sibuco told him that an elderly man escaped the rebels by swimming to the town, where he reported that the rebels had taken captives.

Tapia said his officers were trying to verify the unidentified man's report. Meanwhile, he said, he accepted an offer from the town's parish priest to go to Pangarunan to negotiate the hostages' release.

Tapia and other military officials said they feared the rebels would use their captives as shields to escape advancing government troops.

The fighting was the most sustained since peace talks between the rebels and the government of President Corazon Aquino broke down last May. The talks foundered when the rebels rejected a government offer of autonomy for 13 provinces, subject to a referendum.

A three-member government delegation led by Public Works Secretary Vicente Jayme left for Saudi Arabia on Wednesday to seek help from the 47-nation Organization of Islamic Conference in persuading the guerrillas to resume negotiations.

The Moro National Liberation Front is the largest of three Moslem rebel groups that have been fighting for autonomy or independence on Mindanao and other southern islands for the last 15 years.

About 50,000 people had died in the rebellion when fighting peaked in the 1970s. The rebel activity then dwindled to scattered raids and ambushes.

The Moro Front dropped its demand for independence last December and agreed to negotiate for autonomy. The two other Moslem groups opposed the talks because they were excluded.

Moslems form the majority in five southern provinces, although Roman Catholics are in the majority nationwide.