At least 30 people have died after two explosions at a mosque near the north-eastern Nigerian city of Maiduguri, an emergency official says.

One suicide bomber detonated an explosive inside the mosque in the suburb of Mulai, a regional controller with the National Emergency Management Agency told BBC Hausa.

A second suicide bomber struck as people tried to escape, he said.

The city is often targeted by the Islamist group Boko Haram.

No group has yet said it was behind the attack during Thursday's evening prayers, that left many people injured.

On Tuesday, three bombs exploded in Maiduguri, killing at least four people. Dozens of people were killed in three explosions in the city last month.

Agence France-Presse reported that the death toll could be as high as 42 from Thursday's explosions.