More than 70 people have been killed in a bomb blast at a crowded bus station on the outskirts of Nigeria's capital, Abuja, officials say.
The explosion happened as commuters were about to board buses and taxis to go to work in central Abuja, the BBC's Haruna Tangaza reports.
Eyewitnesses said there were dead bodies scattered around the area.
Suspicion immediately fell on the Boko Haram Islamist militant group, which has staged previous attacks in Abuja.
However, most of its attacks have been in the north-east of the country.
Officials earlier said two separate blasts had ripped through the terminal, but later said the damage may have been caused by just one bomb.
Abbas Idris, head of the Abuja Emergency Relief Agency, told the BBC that so far they have confirmed 71 people dead and 124 injured.
Police spokesman Frank Mba gave the same figures, adding that 16 luxury coaches and 24 minibuses had been destroyed.
Eyewitness Badamasi Nyanya said he had seen 40 bodies being evacuated; other eyewitnesses say they saw rescue workers and police gathering body parts.
Investigators believe the explosives may have been inside a vehicle, according to Charles Otegbade of the Nigerian Emergency Management Agency (Nema).
The blast ripped a hole 4ft deep (1.2m) in the ground of Nyanya Motor Park, some 16km (10 miles) from the city centre, and destroyed more than 30 vehicles, causing secondary explosions as their fuel tanks ignited and burned, the Associated Press news agency reports.
Ambulances have been taking the dead and injured to nearby hospitals.
In a statement, the police said they were on "red alert" and had increased surveillance at "all vulnerable targets within Abuja".
Eyewitness Mimi Daniels, who works in Abuja, said: "I was waiting to get on a bus when I heard a deafening explosion then smoke," she told Reuters.
"People were running around in panic."
Another eyewitness told the BBC: "I have never seen [anything] like that in my life. It was just terrible... We were just running helter-skelter. So somehow I think that they planted something inside one of the buses there.
"So there are many dead shot down at the scene of the accident. And as you can see now some of these casualties... we are hoping, we are praying they will be ok. We saw some ambulances bringing corpses to other hospitals."
No group has taken responsibility for the attack, but Nigerian President Goodluck Jonathan blamed Boko Haram.
Visiting the scene, he vowed that the country would overcome the insurgency.
This year, Boko Haram's fighters have killed more than 1,500 civilians in three states in north-east Nigeria, says the BBC's Will Ross in Lagos.
Boko Haram has hit Abuja several times before, including an attack on the United Nations building in 2011.
The Nigerian government had said the violence was now contained in a small area of the north-east.
But the latest bomb in Abuja could be worrying evidence that the Islamist militants are determined to expand their area of operation, our correspondent adds.