Boko Haram bombers killed 23 people on Thursday (February 26), authorities said, as the Islamist insurgents fight back against a military offensive launched by Nigeria and three neighbouring countries.

A suicide bomber at a bus station in Biu, a town in northeastern Borno state, killed at least 17 people, a military source and local vigilante Ibrahim Jaton said. A crowd beat a second bomber to death before he could detonate his device.

Shortly afterwards, two roadside bombs exploded in the city of Jos in the highly volatile Middle Belt where the largely Christian south meets the Muslim north, killing six people.

"A young man came to Tashan Gandu motor park and our boys stopped him for search at the check point but he refused to stop and all we heard was a loud sound," Jaton said of the Biu blast. "The whole spot was scattered within minutes."

Suicide bombings have become a common tactic for Boko Haram in the last year as the group expanded its control over territory in Africa's biggest oil producer and top economy.

But in the last three weeks Nigeria along with Cameroon, Niger and Chad - all of which have been destabilised by the Islamists - have fought an offensive in border areas.

A spate of Boko Haram attacks on civilians in the past few days seem aimed at striking back.

Police spokesman for Plateau state, of which Jos is the capital, said six people died in the bus station blast.

Garba Musa, a newspaper vendor near the site of the blast said, "There was a loud explosion opposite the university along the Bauchi road, and another one at the Bauchi road motor park."

An increase in violence spreading outwards away from Boko Haram's stronghold in the northeast is a major issue for President Goodluck Jonathan ahead of elections on March 28. He has been accused of not doing enough to protect civilians.

Reacting to Tuesday's bombings Jonathan said "the tide has now definitely turned against Boko Haram".

His main rival former military ruler Muhammadu Buhari told an audience in London on Tuesday he would equip troops better.

Suicide bombers killed at least 26 people at two bus stations in different parts of northern Nigeria on Tuesday, attacks Jonathan blamed on Boko Haram.

On Thursday he visited Baga, which the military recaptured from the insurgents this month, and said they would "receive all the equipment and logistics they require to complete the mission to reassert government's effective control over areas formerly held by Boko Haram", a presidency statement said.

Nigeria's neighbours are being targeted also as they join in the battle against Boko Haram.

Two people on a horse-drawn cart were killed in Niger on Thursday by a mine thought to have been planted by the group. - Reuters