Nigeria's new president, Muhammadu Buhari, will embark on his first official trip overseas this week when he travels to neighbouring Niger and Chad to discuss the fight against Boko Haram, his spokesman said on Monday.

The spokesman, Garba Shehu, told Reuters that Buhari would visit both countries on Wednesday for talks with his counterparts about the militant Islamist group, which has killed thousands and left 1.5 million displaced in Africa's biggest economy over the last six years.

At his inauguration on Friday, Buhari said he would crush Boko Haram and move the command centre for military operations from the capital, Abuja, to Maiduguri, the birthplace of the group's attempt to establish a state adhering to Sharia law.

At least 30 people were killed in Maiduguri over the weekend in two bomb attacks that bore the group's hallmarks.

Troops from Chad, Niger and Cameroon have helped Nigeria's armed forces to push back the insurgents who, at the start of the year, controlled a swathe of territory the size of Belgium in Nigeria, Africa's top oil exporter.

However, the group has maintained a stronghold in the Sambisa forest reserve in the remote northeast of the country.