Two bombs concealed inside a truck and a minibus have killed dozens of people at a crowded market in the central Nigerian city of Jos, military officials said.

"The first IED (improvised explosive device) was in a truck. The second was in a minibus," Kingsley Egbo of the military State Task Force (STF) in Plateau state said on Tuesday.

"The market was really crowded," he added. "We are having a problem of crowd control... The emergency services have evacuated the casualties," he told the AFP news agency.

Al Jazeera's Mohammed Adow, reporting from Abuja, said an exact toll was not immediately clear.

“Details of the incident are scant. Eyewitnesses recounted how twin blasts tore through a busy intersection in between the main market in Jos and a university teaching hospital as well as the main bus station of the town.

"We are being told that there's been no immediate claim of responsibility. However, suspicion will most likely fall on the group, Boko Haram," Adow said.

'Cruel and evil'

President Goodluck Jonathan condemned the blasts, calling the perpetrators "cruel and evil".

"The government remains fully committed to winning the war against terror, and this administration will not be cowed by the atrocities of enemies of human progress and civilisation," he said in a statement emailed by his office.

Boko Haram grabbed world headlines with the abduction of more than 200 schoolgirls a month ago from a remote village in the northeast.

Britain, the United States and France have pledged to help rescue them.

Jos has been relatively free of attacks by the group, but it claimed responsibility for a bomb in a church in the highland city, as well as two other places, on Christmas Day in 2011.

The city is in the heart of Nigeria's volatile "Middle Belt", where its largely Christian south and mostly Muslim north meet, and surrounding Plateau state is often a flashpoint for violence, although the Christmas bomb failed to trigger any.

Tuesday's blasts occurred 15 minutes apart in the afternoon, burning several shops to the ground, shattering windows and spreading rubble in the road.

Police sirens wailed as officers rushed to the scene.

"There was a loud bang that shook my whole house. Then smoke was rising," said Jos resident Veronica Samson. "There were bodies in the streets and people rushing injured to hospital in their cars."

Boko Haram has stepped up its use of explosives in attacks that are spreading far beyond its core area of operation, including two in the capital Abuja last month.

A suicide car bomber killed five people on a street of bars and restaurants in the northern city of Kano on Sunday evening, in an area mostly inhabited by southern Christians.