Agencies are reporting that a series of bomb attacks has killed at least 120 in Kano, Nigeria's second largest city.

The Associated Press reports that the Islamist group Boko Haram had claimed responsibility for the attacks:

A Boko Haram spokesman using the nom de guerre Abul-Qaqa claimed responsibility for the attacks in a message to journalists. He said the attack came as the state government refused to release Boko Haram members held by the police.

Boko Haram has carried out increasingly sophisticated and bloody attacks in its campaign to implement strict Shariah law across Nigeria, a multiethnic nation of more than 160 million people.

Agence France-Presse reports:

Some 20 huge blasts could be heard in the city as a suicide bomber attacked a regional police office and a car bomb rocked the outside of state police headquarters after the attacker fled and was shot dead, police sources said.

A number of other police posts were targeted, including a secret police building, as well as immigration offices.

Gunshots rang out in several areas, and a local television journalist was among those shot dead as he covered the unrest.

"Many agencies are involved in the evacuation of corpses from the streets," a Red Cross source said on condition of anonymity because he was not authorised to speak publicly. "From our tally, we have 121 so far."

Al Jazeera reports that the death toll may be higher:

Other death tolls are higher. Maude Gwadabe, a journalist in Kano, told Al Jazeera by phone that he had seen at least 140 dead bodies.

Al Jazeera has more with video: