Philippine friendly fire airstrikes kill 11 troops

Marawi : Philippine airstrikes aimed at Islamist militants who are holding hostages as human shields in a southern city killed 11 soldiers, authorities said Thursday, as they conceded hundreds of gunmen may have escaped a blockade.

The friendly fire deaths bring to 171 the number of people reported killed since gunmen waving black flags of the Islamic State (IS) group began rampaging through the Muslim city of Marawi last week.

Shortly after the violence erupted President Rodrigo Duterte imposed martial law across the southern region of Mindanao, home to 20 million people, to quell what he said was an IS bid to establish a base in the mainly Catholic Philippines.

But the government's narrative of being in "full control" of Marawi took a hit Thursday when defence chiefs said 11 soldiers were killed in a misguided bombing mission.

"It's very painful. It's very sad to be hitting our own troops," Defence Secretary Delfin Lorenzana told reporters in Manila.

"It's sad but sometimes it happens in the fog of war."

He initially said 10 soldiers died but national military spokesman Brigadier-General Restituto Padilla later confirmed 11 were killed.

Lorenzana also warned that many militants may have escaped, despite checkpoints throughout the city and surrounding it.

"We have reports they are going to some of the towns around Marawi city," Lorenzana said.

He said there were about 500 militants at the start of the unrest and only between 50 and 100 were believed to still be in Marawi. According to the military, 120 gunmen have been killed, meaning as many as 330 remain unaccounted for and could have slipped out of the city.

Adding to concerns about the rising threat of IS, Lorenzana said militants from Saudi Arabia, Chechnya, Yemen, Malaysia and Indonesia were among the dead.