A founder of an Islamic group blamed for the worst militant attack in the Philippines has been arrested while working at a Philippine embassy in the Middle East, officials said on Saturday.

Ruben Lavilla, also known as Sheik Omar Lavilla, was deported back to Manila on Saturday, more than a month after he was arrested in Bahrain. His arrest was not made public.

Marcelino Libanan, head of the immigration commission, said Lavilla was trying to get a loan from a local bank in Bahrain when some of the documents he had submitted set off alarm bells in the tiny oil-rich state.

"It took us a month to bring him back," Libanan told reporters, referring to the deportation proceedings.

He said the 35-year-old militant leader was working as an editor of a local magazine and was also hired as an interpreter at Manila's embassy in Bahrain.

Fernando Mesa, executive director of the government's anti-terrorism council, said Lavilla was wanted for the Christian-majority country's worst militant attack, the bombing of a ferry near Manila Bay in 2004, in which more than 100 people were killed.

Mesa, a retired general, said Lavilla was the "brains" of the Rajah Solaiman Movement, a violent Islamic militant group blamed for several bomb attacks in Manila in 2004 and 2005.

It is affiliated to the Abu Sayyaf group of radicals, notorious for kidnappings and bomb attacks.

Lavilla, an Islamic scholar, was the spiritual leader of the group and is believed to have taken it over after its two top leaders were arrested in the south in 2006.

Mesa said others in the group were believed to have joined the Abu Sayyaf, which is largely based on Jolo island, off the Mindanao mainland in the south.

On Saturday, four soldiers were killed and 10 were wounded when suspected Abu Sayyaf rebels ambushed a convoy of Marine soldiers near Patikul town on Jolo island, the military said.

In Mindanao, fighting is continuing between the military and a group of renegades from the Moro Islamic Liberation Front (MILF), the country's biggest Muslim rebel group.

The MILF was holding peace talks with the government but some of its members went on the rampage earlier this month after the Supreme Court blocked a territorial agreement between the two sides.

Nearly 200 people have been killed in almost two weeks of fighting on Mindanao, the military has said.-Reuters