At least 82 people have been killed in two bombings in the northern Nigerian city of Kaduna.

The blasts targeted opposition leader and former president Muhammadu Buhari at a busy market and a moderate Muslim cleric about to lead a crowd in prayer.

The attacks have the hallmarks of Islamist group Boko Haram but may also have been linked to political friction ahead of elections due in 2015.

The deadlier blast targeted Mr Buhari's convoy at the crowded Kawo market, his son told Reuters at the scene. Mr Buhari was riding in an armour-plated vehicle and was not wounded.

However at least 50 people were killed there, according to a Red Cross official.

Mr Buhari was the main opposition party contender against Nigerian president Goodluck Jonathan in the 2011 election and remains a key figure in the opposition alliance.

After the blast a crowd gathered at the scene but were dispersed by the military firing shots into the air.

Suicide bomber targets moderate cleric, blast kills dozens

Earlier, a suicide bomber targeting a moderate cleric killed at least 32 of his congregation on a busy commercial road.

Thousands were gathered for prayers with Sheikh Dahiru Bauchi in Murtala Muhammed square.

When his convoy arrived, the bomber lunged at him before being stopped by his private security, witnesses and police commissioner Shehu Umar Ambursa said.

"Somebody with a bomb vest ... was blocked. He detonated the bomb along with the person that tried to block him," the police commissioner said.

Police have confirmed 25 dead, with 14 wounded. Police sometimes give lower casualty tolls than workers on the scene.

The bomber did not injure the cleric, several witnesses said.

Some followers had come from Senegal, Chad and Niger to see the popular sheikh.

An angry crowd started throwing stones at police, who responded with tear gas.

Kaduna's governor Mukhtar Yero declared a 24-hour curfew in the city until further notice and condemned the bombings as "the height of cowardice".

"The enemies of peace have visited us with their ungodly venom of wanton destruction," he said in a statement.

"Those behind the act have no notion of God, as they have none for the sanctity of human life."

Reuters