Bombs exploded at two major military bases on the outskirts of the Nigerian city of Kaduna yesterday, injuring an unknown number of people.

The attacks came as a radical Islamist sect known as Boko Haram continued to launch increasingly bloody attacks on the government. No one has claimed responsibility for the bombings.

The blasts struck at the Nigerian army's 1st Mechanised Division headquarters and the training command of the Nigerian air force.

A third explosion took place near a highway overpass, though officials had no other details about it.

Witnesses said they saw injured soldiers wearing blood-drenched uniforms after the blasts.

A spokesman for the 1st Mechanised Division, Lieutenant-Colonel Abubakar Edun, said two cars loaded with explosives rammed through the headquarters' gates. Only one detonated, he said.

Army spokesman Major General Raphael Isa said one of the suicide bombers was dressed in a military uniform.

Soldiers guarding the gate opened fire on the man, who died from gunshot wounds.

"The suicide bomber was the only casualty," Isa said.

Kaduna, on Nigeria's dividing line between its largely Christian south and Muslim north, was at the heart of post-election violence in April. Mobs armed with machetes and poison-tipped arrows took over the streets and countryside after election officials declared President Goodluck Jonathan the winner. Followers of his main opponent, Muhammadu Buhari, a Muslim, quickly alleged the vote had been rigged, though observers largely declared the election fair.

Boko Haram's members have been blamed for killing at least 270 people this year alone.