Two blasts have rocked bus stations in embattled northern Nigeria, killing at least 27 people, as relentless attacks persist less than five weeks from general elections.
The first explosion, which killed 17 people, was caused by a bomb that ripped through a station on the outskirts of Potiskum, in northeast Yobe state, which has been targeted repeatedly by Boko Haram Islamists.
Roughly four hours later, two men blew themselves up after getting off a bus at a busy terminus in Kano, the north's largest city and another frequent Boko Haram target, killing 10 people.
The Nigerian militant group has been blamed for more than 13,000 deaths since 2009 and has in recent weeks expanded its uprising into neighbouring countries, raising fears of a regional crisis.
In Niger on Tuesday, a mine planted by the insurgents killed two soldiers and injured four others in the Diffa region bordering Yobe, a security source said.
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Niger this month joined Cameroon, Chad and Nigeria in a joint operation aimed at crushing Boko Haram's uprising and many expected the Islamist rebels to launch cross-border reprisals.
Nigeria had hoped the four-nation offensive could contain the violence before elections initially scheduled for February 14, but which were postponed by six weeks because of the insurgency, however, with the bloodshed continuing on a nearly daily basis, security fears remain high ahead of the March 28 vote.
The Potiskum explosion occurred at the Tashar Dan-Borno motor park on the outskirts of the city immediately after a man put a bag in the boot of the bus and then tried to board.
Potiskum was also attacked on Sunday, when a young girl detonated explosives strapped to her body at a crowded market.
Thirteen dead and 31 injured were initially brought to Potiskum General Hospital after Tuesday's blast, according to a nurse at the facility, but she added, "Four more died here, so we have 17 dead and 27 people with injuries."
A drivers' union official says it was not immediately clear whether the man who placed the bag in the boot was a suicide bomber, or whether the explosives were hidden inside it.
Rescue workers at the scene said that all 12 people on board the bus were killed.
The girl in Sunday's attack which left seven people dead in Potiskum was thought to be as young as seven, according to multiple witnesses.
