At least 71 people were killed when a parked vehicle exploded at a bus station in the Nigerian capital, Abuja, on Monday morning, Nigerian officials said.

Another 133 people were injured in the explosion on the outskirts of the city, national police spokesman Frank Mba said.

The attack happened at about 6.45 a.m., as the Nyanya Motor Park bus station was crowded with early morning commuters. One first responder at the scene told CNN "bodies were scattered everywhere."

"We're still treating people with injuries and collecting data," said Ishaya Isah Chonoko, zone coordinator at the National Emergency Management Agency in Abuja.

Information about what caused the blast wasn't immediately available. Charles Otegbade, the emergency management agency's search and rescue chief, said the explosion came from a vehicle that was parked at the station.

Interpol, which has offered its assistance to the team investigating the explosion, condemned what it called a "senseless and cowardly terrorist attack."

"This slaughter of innocent members of the public will have appalled citizens of all countries," the organization's Secretary General Ronald K. Noble said in a statement. "Interpol condemns this mass murder in the strongest possible terms and we express our solidarity with the people of Nigeria at this difficult time."

No individual or organization has so far come forward to claim responsibility for the blast, but it is believed to bear the hallmarks of Boko Haram, an Islamist militant group that has waged a campaign of violence in Nigeria in recent years.

Visiting the scene of the explosion, Nigerian President Goodluck Jonathan spoke of overcoming the militants.

"The issue of Boko Haram is quite an ugly history within this period of our own development ... but we will get over it," he said. "... The issue of Boko Haram is temporary."

Nigeria's Islamist insurgency has claimed more than 3,000 lives since it began in 2009, according to Human Rights Watch.

Boko Haram, which means "Western education is sacrilege" in West Africa's Hausa-Fulani language, is fighting for the imposition of stricter Sharia law across the country, and has launched a self-styled "war on Christians" in Nigeria.

The group is designated a "terrorist organization" by the U.S. State Department;

U.N. refugee agencies estimate that more than 8,000 Nigerians have fled into neighboring Cameroon to escape escalating violence sparked by the militants, while another 5,000 have become internally displaced.

Until now, Boko Haram's focus has mainly been concentrated on areas of Nigeria's northeast, where the group has launched bomb, gun and arson attacks on homes, schools, markets and even whole villages.

But it is not the first time Abuja has been targeted; in 2011 a Boko Haram suicide attack on the United Nations building in the city killed at least 25 people.

Security forces in the capital are now said to be on alert after Monday's blast in Abuja raised concerns the insurgency could be spreading further afield.