Nigeria’s main relief agency on Monday warned of high casualties a day after multiple explosions blamed on Boko Haram militants hit the restive northeastern city of Maiduguri.

Nigeria's main relief agency on Monday warned of high casualties a day after multiple explosions blamed on Boko Haram militants hit the restive northeastern city of Maiduguri.

The blasts happened shortly after 7:20 pm (1820 GMT) on Sunday in the Gomari and Ajilari areas of the city, said Ibrahim Abdulkadir, spokesman of the National Emergency Management Agency (NEMA).

Abdulkadir was not able to give an exact death toll but he added: "The casualty is high. One of the explosives was planted in a mosque where people were praying."

Nigeria's military confirmed three bombs went off in the city but also did not give any casualty figures.

"Although details are not clear, it is important to note the attacks signify high level of desperation on the part of the Boko Haram terrorists," army spokesman Sani Usman said.

Local residents spoke of hearing at least two explosions within a few minutes of each other in the restive city's densely-populated Binta Sugar area.

Maiduguri, the capital of Borno state and the birthplace of Boko Haram in 2002, has been the epicentre of the six-year-old insurgency.

The violence has left at least 17,000 dead since 2009, according to Amnesty International, while the UN estimates that more than two million have been made homeless in the same period.