A car bombing near a church in the northern Nigerian city of Kaduna on Easter Sunday killed dozens of people, while another blast later in a separate city caused a number of injuries.
At least 38 people were killed in the blast in Kaduna, Abubakar Zakari Adamu, a spokesman for the Kaduna state's Emergency Management Agency told the Associated Press.
The deadly explosion in Kaduna, an important cultural and economic centre in Nigeria's north, was a stark reminder of Christmas Day attacks that left dozens of people dead in Africa's most populous nation and largest oil producer.
Hours later a second explosion hit Nigeria's central town of Jos, causing a number of injuries, an emergency agency said.
Jos sits on the dividing line between Nigeria's mostly Muslim north and largely Christian south and religious and ethnic clashes regularly flare up.
Boko Haram suspected
The explosion in Kaduna occurred on a main road where motorcycle taxi drivers and passers-by caught much of the blast.
No one claimed reponsibility for the blast, but authorities suspect radical group Boko Haram, which has carried out similar attacks in the past.
Al Jazeera's Yvonne Ndege, reporting from the scene of the Kaduna attack, said things had calmed down considerably after authorities and medical officials had earlier been evaluating the damage.
At least one car said to be driven by a suicide bomber was involved in the attack, which according to initial reports had taken place near a church.
"I'm standing just at the scene where this car exploded and contrary to initial reports, it now looks like this car bomb did not actually detonate outside a church which had been earlier reported," Ndege said on Sunday.
"What it looks like is that these individuals, clearly suicide bombers, were on their way to potentially a location where they intended to explode their devices.
"Something clearly went wrong because if you look at the area where this car bomb went off it's in the middle of the main road which would have had heavy traffic on Easter Sunday and many ordinary people standing on the side of the road selling their wares.
A rescue official told the AFP news agency that two vehicles packed with explosives had detonated, but this report remains unconfirmed.
A police officer at the scene earlier said a man believed to be a suicide bomber driving a car was stopped at a checkpoint near a church and turned back, but drove to a nearby area close to a hotel and detonated the bomb.
Other cars in the area were damaged, but it was unclear if they were also carrying explosives, he said.
Police confirmed the explosion was a bomb, but did not officially comment further.
"We have a bomb explosion. We are trying to sort things out," Aminu Lawal, a police spokesperson, told AFP.
Residents reported seeing dead and injured people being taken away.
One resident said the explosion was strong enough to shake his house and cause his ceiling to cave in.
"People have in one sense been bracing themselves for something, because the army, the joint task force who have been dealing with Boko Haram primarily have warned of the threat of attacks," our correspondent said.
Boko Haram set off a series of bombs across Nigeria on Christmas Day last year, including one at a church outside the capital Abuja that killed at least 37 people and wounded more than 50.