Two explosions went off Friday outside a customs building in Nigeria's flashpoint city of Maiduguri, the base of Boko Haram Islamists blamed for a series of attacks, residents said.

"I was in a taxi going home when the first bomb exploded... (Within) just two minutes, another one ahead of us went off," said resident Babagani Ari, whose account was supported by other locals in the northeastern city.

The spokesman for a special military squad established to crack down on Boko Haram in the area confirmed the explosions.

"We have deployed our field men to the scene of the blast, and I will have to wait for the briefing before I can say anything," said Hassam Mohammed, spokesman for the Joint Task Force in Maiduguri.

The explosions went off near a station where locals board rickshaw taxis, located outside the customs building, witnesses said.

"The first bomb was planted at the foot of the wall of the customs office when commuters were waiting for rickshaws," said Halilu Adam.

"The second one went off some meters away... The whole area has now been cordoned off by soldiers and it is very difficult to have an idea of casualties."

Boko Haram has claimed attacks that have killed more than 200 people this year in several parts of Nigeria. The group has largely targeted police and other symbols of authority.