Bomb kills 19 people near a checkpoint, days before city is to host the World Economic Forum on Africa

The death toll from a car bomb that exploded on a busy road in the Nigerian capital, Abuja, has risen to 19, police have said.

The bomb was detonated on Thursday at a congested checkpoint near a bus station where two weeks ago an explosion claimed by the Islamic extremists Boko Haram killed at least 75 people.

The latest attack comes days before Abuja is to host the World Economic Forum on Africa, with the Chinese premier, Li Keqiang, among the guests. The government is deploying 6,000 police to protect the event, which attracts world leaders, policymakers, philanthropists and business leaders to discuss Africa's economic growth prospects.

Witnesses said a car laden with explosives drove close to the checkpoint and a man jumped out and ran as it blew up. The explosion was followed by several smaller ones as other cars caught fire and ignited.

Lines of traffic are normal at the checkpoint, where soldiers and police have been searching vehicles since the 14 April bombing.

Police superintendent Frank Mba said on Friday that the death toll had risen to 19, with as many wounded being treated in the hospitals. Six cars were destroyed in the blast, he said.

Two unexploded IEDs were found at the scene, according to a security official. Militants in Nigeria often time secondary explosions to target rescuers and others drawn to a bombing.

While there was no immediate claim for Thursday's bombing, it bears all the hallmarks of Boko Haram. The group wants to create an Islamic state in Nigeria, which it claims would halt crippling corruption that keeps 70% of the people in Africa's richest nation impoverished.

Hours after the 14 April bombing, which wounded at least 141 people, Boko Haram militants kidnapped more than 250 teenage girls at a school in the remote north-east, which is their stronghold. About 50 of the girls escaped their captors but 200 remain missing.

President Goodluck Jonathan told a May Day rally in Abuja earlier on Thursday that the perpetrators must be brought justice. "We shall triumph over all this evil that wants to debase our humanity or obstruct our progress as a nation," he vowed. "Those who want to re-define our country to be seen as a country of chaos will never succeed."

Last week, he assured the Chinese ambassador that the hundreds of delegates expected at the World Economic Forum on Africa "will not have a problem with security during the summit".