Nigerian officials say at least three bombs exploded in the northeastern city of Maiduguri on Friday.

Witnesses say the blasts took place within a short period of time in the volatile city, where the government has blamed increasing violence on the radical Islamist sect Boko Haram.

Authorities say one of the explosions took place at an Islamic college where people had gathered for Friday prayers.

Security officials say another one targeted a military compound which is home to a unit charged with protecting the city from Boko Haram.

It was not immediately clear if there were casualties.

On Thursday, military officials said troops in Maiduguri had started searching homes for illegal weapons that could be used by the sect.

The sect does not recognize Nigeria's government or constitution and claims it is fighting to create a new country ruled by strict Islamic law.

In July of 2009, Boko Haram launched a brief uprising against the government, prompting a heavy military response that killed about 700 people in one week of fighting.

More recently, the shadowy group has carried out a series of bombing and shootings. In August, it claimed responsibility for bombing that killed 24 people at the Abuja headquarters of the United Nations.

Boko Haram means “western education is a sin” in the native Hausa language.