'Isil invasion' in the Philippines: Indonesians and Malaysians among foreign jihadists laying siege to city

Indonesians and Malaysians were among foreign Jihadists battling the military after laying siege to a southern Philippine city, the government said on Friday, in a rare admission of what it said was an Isil "invasion".

The army has deployed attack helicopters and special forces to drive rebels of the Islamic State of Iraq and the Levant-linked Maute group out of Marawi City and Malaysians and Indonesians and other foreigners were among six guerrillas killed on Thursday.

The announcement elevates the threat of what experts and the military say are moves by Isil to exploit the poverty and lawlessness of predominantly Muslim Mindanao island to establish a base for extremists from Southeast Asia and beyond.

"What's happening in Mindanao is no longer a rebellion of Filipino citizens," Solicitor General Jose Calida told a news conference.

"It has transmogrified into invasion by foreign terrorists, who heeded the call of the ISIS to go to the Philippines if they find difficulty in going to Iraq and Syria," he said, using another acronym for Isil.

President Rodrigo Duterte has delivered on his threat to impose martial law on Mindanao, the country's second-largest island, to stop the spread of radical Islam.

He has been pleading with Mindanao governors and religious leaders to work with the government to keep extremists at bay.

Mr Duterte recently warned that Islamic State fighters driven from Iraq and Syria would end up in the southern Philippines and his country was at risk of "contamination".

The Maute, which has pledged allegiance to Isil, held its positions on bridges and buildings on Friday as ground troops launched early morning offensives to flush out the remaining gunmen after unrest that has killed 11 soldiers and 31 militants.

The White House on Thursday said it backed the Philippines in its fight against "cowardly terrorists".

Few of Marawi's 200,000 inhabitants remained after militants ran amok, seizing and torching schools, a college and a hospital. They freed more than 100 prisoners and took a priest and churchgoers hostage at the city's cathedral.