Two female suicide bombers blew themselves up killing at least ten people on Tuesday in a crowded market area of Nigeria's northeastern city of Maiduguri, center of a militant islamist insurgency, witnesses said.

Four witnesses told Reuters near the scene that a woman had entered the roadside trading area behind the city's main market before blowing herself up.

"While the people were trying to help the injured the second bomb blasted," witness Sani Adamu told Reuters. "I saw lots of bodies".

Nigerian authorities did not immediately respond to requests for comment. There was no claim of responsibility, but suspicion is likely to fall on violent Islamist group Boko Haram, whose 5-year-old campaign for an Islamic state has killed thousands.

Using female suicide bombers has become a growing tactic of the group.

Adamu said he counted more than 30 people on the ground, but did not know if they were dead or wounded.

Another three witnesses said at least 10 were killed in the blasts. Police cordoned off the scene and sirens wailed in the aftermath.

"I counted ten dead bodies on the ground before the police arrived," Muhammadu Garba, a trader, told Reuters.

A source at Maiduguri's General Hospital said five bodies had already arrived from the scene.

Nigerian President Goodluck Jonathan plans to ask the national assembly to extend a state of emergency in three northeastern states worst hit by the insurgency when it expires this week.