Two car bombs ripped through a crowded market in the central Nigerian city of Jos on Tuesday, the latest in a series of deadly blasts, as a state of emergency was extended in the troubled northeast.

The blasts happened at the New Abuja Market, the spokesman for the Plateau state governor, Pam Ayuba, told AFP. An unconfirmed report from one eye witness said at least seven people were killed.

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

Plateau, of which Jos is the capital, falls in Nigeria's so-called Middle Belt, where the mainly Christian south meets the Muslim-majority north.

The state and its religiously divided capital have seen deadly sectarian clashes in the past but has also been hit by violence from Boko Haram extremists.

The bombings follow two separate attacks on the same bus station in a suburb of the capital, Abuja, on April 14 and May 1, that killed more than 90 people. The first was claimed by Boko Haram.

Four people were also killed on Sunday in a suicide car bomb attack in a predominantly Christian area of the northern city of Kano that had been previously targeted by the group.

There was no immediate indication of responsibility for the latest strike but the police said two men were arrested at a bus station after being overhead discussing the Kano bombing.

The blasts in Jos happened after senators in the upper chamber of parliament gave their unanimous approval for a six-month extension to a state of emergency in three northeast states.

The lower House of Representatives overwhelmingly backed the plan in a vote last week.

President Goodluck Jonathan had requested a continuation of special powers in Borno, Yobe and Adamawa because of what he said was the "daunting" security situation and mounting civilian casualties.

The approval -- the second since special powers were first introduced on May 14 last year -- came as no surprise, with more than 2,000 people killed this year alone.

It also came as international teams help in the search for more than 200 schoolgirls abducted from the remote Borno town of Chibok on April 14 that has led to global outrage.

In approving their request, the senators said they "welcome and endorse the support of the international community" in the search, which includes the United States, Britain, France and Israel.

The senators called on Jonathan, who has been criticised for his lacklustre response to the mass kidnapping, to expand co-operation to bring an end to the violence.

They also urged for a "full military operation" to be conducted to crush the insurgents as well as non-military means to tackle the roots of the rebellion in the impoverished north.

The Boko Haram insurgency is Nigeria's most pressing security concern and has prompted fears that it could spread to neighbouring countries after sporadic attacks in Cameroon, Chad and Niger.

Regional leaders agreed at a summit in Paris on Saturday to improve their co-operation, including by better surveillance and intelligence sharing, to end the violence.

In Nigeria, where there have been widespread concerns about the safety of schoolchildren, the police said they were beefing up security at boarding schools to prevent a repeat kidnapping.

"The Inspector General of Police, MD (Mohammed) Abubakar, has ordered command commissioner of police to immediately commence (a) security audit and threats analysis of all boarding schools nationwide," a statement read.

Senior officials said they expected the results to help determine security strategies to reduce the vulnerability of schools, which have previously been seen as soft targets for the extremists.

Earlier this month, the United Nations' special envoy for global education, British former prime minister Gordon Brown, announced a "Safe Schools Initiative" to improve security at an initial 500 schools in the north.