An apparent car bomb at a Nigerian bus station has killed at least 71 people and injured more than 120 others.
President Goodluck Jonathan visited the bus terminal on the outskirts of the capital, Abuja, several hours after the bomb went off during Monday morning rush hour.
The president urged Nigerians to be vigilant about suspicious movements, and suggested Islamist militant group Boko Haram was behind the blast, although there has been no claim of responsibility.
"We console with our country men and women, we will continue to work very hard. The issue of Boko Haram attacks is quite an ugly history within this period of our own development. We will do everything to make sure that we move our country forward. These are unnecessary distractions that are pushing us backward.''
The News Agency of Nigeria quotes a survivor, Prince Igwe, as saying the blast came from a vehicle parked in front of several buses filled with passengers.
The man, who said he was in one of the buses, says the driver of the car parked quickly, then disappeared shortly after the explosion.
A police spokesman says some 40 vehicles were damaged or destroyed in the blast.
An adviser to President Jonathan, Reuben Abati, says all of Nigeria's security services are working together to investigate the bombing.
"The investigations are continuing and [they are] an inter-agency collaborative effort. All the various security agencies are involved; the police, the civil defense, the state security services and the various intelligence agencies of the military. When the incident occurred, one of the perpetrators was also caught up in the explosion and he died. Some of the media houses have shown the pictures of the suicide bomber."
Boko Haram has attacked many public places such as markets and schools, although most of the attacks have taken place in Nigeria's Muslim-majority north.
The militants are suspected in weekend attacks that killed at least 60 people in Borno state. Nigerian newspapers report the assailants attacked two villages at night, killing residents in their homes and setting fire to houses and shops.
The shadowy Boko Haram has said it wants to create a strict Islamic state in northern Nigeria. The group has been blamed for thousands of deaths since launching an insurgency against the government in 2009. Efforts by Nigeria's military to contain the group have done little to stop the violence.