A group of heavily-armed militants from a group linked to Isis have reportedly stormed a city in the Philippines and engaged in firefights with the national army.

Residents of Marawi City, in the south of the country, were urged to remain indoors as at least 15 gunmen from a Muslim rebel group called Maute stormed the streets brandishing assault rifles.

The group, which is also known as the Islamic State of Lanao, have reportedly received support from Isis.

Troops and a special police force were deployed to the city after residents in a nearby village raised the alarm and appealed for help.

President Rodrigo Duterte then declared martial law and a state of emergency in the province of Mindano. General Eduardo Ano, the military chief of staff, said at least one police officer was killed and eight soldiers were wounded in the fighting.

“I’m appealing to residents of Marawi City to stay home, drop on the ground if they hear gunshots," Mamintal Adiong Jr, the governor of the ​Lanao del Sur province told The Philippine Star newspaper. "They have to lock their doors and gates too."

Local reports suggested that the militants had entered a local hospital and raised a black Isis flag above the roof, although this information was officially verified by the army.

Witnesses reported seeing men in attire similar to that worn by Isis militants walking the streets before firing at houses and government buildings.

"There [were] no indications that an attack like this will happen. There are no checkpoints in the city," one resident said. "Everything is in silence. No news about the city government. Everything is vague."

Vice governor Mamintal Adiong Jr, a senior member of the Marawi council, said that local emergency response teams from across the region had been mobilised to help residents trapped in the crossfire.

In March, President Duterte pleaded for help from mayors in Muslim areas of the south of the country to deal with Islamist militants, and threatened to impose martial law there if the problem was not tackled.

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Last year the president pledged to ignore human rights if the breakup of Isis in the Middle East worsened the Islamist insurgency in his country.

The Maute is a radical Islamist group composed of former Moro Islamic Liberation Front guerrillas and some foreign fighters.

They are thought to have taken their name from its founder Abdullah Maute.