FILIPINO President Rodrigo Duterte has asked Moro — Muslim Filipino — and communist rebels to join the fight against the country’s Isis affiliate.

The unprecedented move on Sunday came ahead of a Supreme Court challenge by six opposition congress members yesterday to Mr Duterte’s declaration of martial law in the southern island of Mindanao.

Troops are fighting Isis-affiliated Abu Sayyaf extremists who seized the city of Marawi, the largest city in the province of Lanao del Sur on the island, two weeks ago.

Congressman Edcel Lagman, leader of the six, said the the state of emergency was unjustified as there had not been a revolution or invasion.

Several foreign jihadists have been identified among militants killed in the battle to recapture the city of 200,000 residents, almost all of whom have fled.

On Sunday Mr Duterte said he had accepted an offer from Moro National Liberation Front (MNLF) chairman Nur Misuari to integrate 2,000- 3,000 guerillas into the government’s forces to help fight the Maute group, Abu Sayyaf’s strongest ally.

And he called on the Moro Islamic Liberation Front (Milf) and the communist New People’s Army (NPA) to follow suit.

“If you want to join us, you are also invited, including the regulars of the NPA,” he said. “Just bring the guns, I will replace them with new ones and you’ll be enlisted in the armed forces.”

Last Monday Mr Duterte met Milf leaders in the southern Mindanao city of Davao.

A Milf statement the following day said chairman Al Haj Murad Ebrahim welcomed sending its forces “to help in extending necessary humanitarian assistance to civilians still trapped in areas of Marawi.”