BOKO Haram militants dressed as soldiers have killed at least 200 civilians in three communities in north-eastern Nigeria, with witnesses claiming the military failed to intervene.

A community leader who witnessed the attacks on Monday said residents of the Gwoza district in Borno state had pleaded for the military to send soldiers to protect the area after they heard militants were about to attack, but help did not arrive.

It took a few days for survivors to get word of the attack to Maiduguri, the provincial capital, because road travel is dangerous and phone connections are poor.

The massacres were confirmed by Mohammed Ali Ndume, a senator representing Borno whose home town is Gwoza, and a senior security official in Maiduguri.

Militants of Boko Haram, which wants to establish an Islamic state in Nigeria, have been taking over villages in the north east, killing and terrorising civilians.

It is currently holding hundreds of schoolgirls captive after snatching them from their school the remote village of Chibok in April.