Officials say Philippine troops, backed by attack helicopters and artillery fire, battled with at least 250 Abu Sayyaf militants in the country's restive south, leaving two soldiers and six militants dead.

Military spokesman Lt. Col. Harold Cabunoc said Thursday's heavy fighting in Sulu province's Patikul township wounded 15 soldiers and 10 rebels.

He says sporadic fighting continued hours after the first close-quarter firefight in the morning, and rebels were seen carrying away at least six dead.

It was not immediately clear why there was a large gathering of militants. Abu Sayyaf's force has dwindled to around 400 fighters.

Cabunoc says the group troops encountered may have included relatives of militants.

He says the rebels could be planning a huge-scale attack or were gathered for a wedding.