MANILA (REUTERS) - The Philippines has received intelligence that shows closer links between domestic militants and militants from Islamic State in Iraq and Syria (ISIS), its defence minister said on Thursday (Jan 26), adding weight to worries that Middle East extremists are building a network in South-east Asia.

Intelligence from allies showed a leader of the Abu Sayyaf militant group, which has gained notoriety for piracy and kidnapping in the southern Philippines, trying to spread into new areas of the Philippines upon the instruction of ISIS, according to Defence Secretary Delfin Lorenzana.

"Isnilon Hapilon left his traditional area of operation on Basilan island and went to Lanao del Sur to see the area and find out if it is conducive for them to move there," Mr Lorenzana told a news conference, referring to an Abu Sayyaf leader.

Lanao del Sur is a province on the main southern island of Mindanao, to the north-east of the much smaller Basilan island.

Lanao del Sur is a stronghold of a the Maute rebel group, which has also pledged allegiance to ISIS. Several of its members have been arrested for a bombing last year in which 14 people were killed.

Mr Lorenzana did not say which country provided the intelligence, but said it included information that Hapilon had made the move to survey the new area "at the behest" of ISIS.

The army had until recently denied the existence of links between ISIS and Muslim militants in the Philippines, and said Abu Sayyaf had only pledged allegiance to the network to boost its profile.

Abu Sayyaf, which operates in two southern islands, has kidnapped dozens of foreigners over recent years and beheaded several of them, including two Canadians last year.

The United States has a US$5 million (S$7.1 million) bounty on the head of Hapilon for leading the 2001 kidnapping of 20 people, including three Americans, on a resort island. He has been identified as Abu Sayyaf's commander on Basilan.

President Rodrigo Duterte has recently raised the alarm about the prospect of ISIS "contaminating" the Philippines if driven out of Iraq and Syria.

"They were communicating before but not as much as what they are doing now when ISIS in the Middle East are having trouble retaining their areas," Mr Lorenzana said, referring to contacts between Abu Sayyaf and ISIS.

Philippine forces on Thursday dropped bombs and fired shells at rebel positions in the mountains of Lanao del Sur in a bid to flush out Hapilon, Mr Lorenzana said.