At least eight civilians, including three women and two children, were killed when Philippine troops raided a coastal village on a remote southern island, local officials said on Tuesday.

They said the civilians were killed during a pre-dawn mission on Monday by U.S.-trained navy commandos to rescue two hostages held by the Abu Sayyaf, a small radical Islamic rebel group.

"We condemned this dastardly act," said Abdusakur Tan, governor of Jolo island, where flags were being flown at half mast in a mark of mourning.

"We're calling for a full-blown investigation to let those culprits face justice."

The island's military commander, Major-General Ruben Rafael, acknowledged eight civilians were killed and investigations were on to ascertain what happened.

Rafael said the bodies of the eight civilians were found away from the site of the operation, suggesting that they were killed in another incident. Jolo has a tradition of clan warfare.

"It was a legitimate operation and we're trying to find out how those civilians got killed," he said.

Two commandos and three Islamic militants were killed in a military operation in the area at the same time.

But local officials, citing residents, said the commandos opened fire on civilians after being shot at as they arrived for their operation near Maimbung town.

Tan said he was informed by a village chief and some residents that one of those killed on Monday was a soldier on vacation.

"He was tied up and shot in front of his wife. Some of the civilians were shot in the head. These people were not caught in the crossfire, they were the targets."

Officials said they were still trying to account for all the residents.

Jolo, a Muslim island 600 miles (950 km) south of Manila, was once touted as a success story in the Philippine military's battle to flush out the Abu Sayyaf and a handful of foreign jihadists.

But the Abu Sayyaf resumed kidnapping and decapitations last year and relations with the locals have deteriorated due to military operations that have forced villagers from their homes.