A series of explosions on the outskirts of the Nigerian capital Abuja have killed at least 18 people, officials say.

The first two struck Kuje township: one by a suicide bomber near a police station, the other a bomb at a market.

Another bomb exploded at a bus stop in Nyanya.

No group has said it carried out the attacks yet but suspicion has fallen on Boko Haram Islamists, who targeted Nyanya last year.

The militants, who are fighting to carve out an Islamist state, has mostly focused their campaign on the north-east.

More than 40 people were injured in the blasts on Friday night, which security officials described as co-ordinated.

Explosives experts have been combing the scene for bomb fragments.

Police have also stepped up stop-and-search activities in Abuja following the blasts, AFP reported.

Nigeria's President, Muhammadu Buhari, who came to power vowing to eradicated Boko Haram, condemned the attack.

"My heart goes out to the families of the dead and injured in Abuja, and other parts of the country. Our will cannot be broken; evil will never triumph over good. We will be rid of this evil stalking our land," he tweeted.

Some 17,000 people are said to have been killed since Boko Haram began its insurgency in 2009.

This year, security forces have managed to reclaim most of the territory captured by Boko Haram fighters and freed a number of people kidnapped but militant attacks have intensified.