MANILA — The Philippines has received intelligence reports showing closer links between domestic militants and the Islamic State group, the defense department said on Thursday, adding weight to worries that Middle East extremists are building a network in Southeast Asia.

Intelligence from allies showed a leader of the Abu Sayyaf militant group, which has gained notoriety for piracy and kidnapping in Mindanao, was trying to spread into new areas of the country upon the instruction of Islamic State, according to Defense 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," 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 northeast of the much smaller Basilan island.

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 Islamic State.

The army had until recently denied the existence of links between Islamic State and Muslim militants in the Philippines and said Abu Sayyaf was 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 $5-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 Islamic State "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," Lorenzana said, referring to contacts between Abu Sayyaf and Islamic State.

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

Government 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, Lorenzana said.