An explosion at a major bus station in Gombe state has killed at least four people and injured 32, police say.
According to a BBC report, Gombe city hospital sources say the casualty figure is higher and a bus park official says 13 vehicles were destroyed in the rush-hour blast.
Police say explosives were concealed in a bus and three men have been arrested.
Gombe shares a border with three states placed under emergency rule to fight the Boko Haram Islamist insurgency.
The group has taken full control of Mubi, a commercial centre in Adamawa.
It is the largest town Boko Haram has taken since it stepped up its insurgency when the state of emergency was declared in May 2013 in Adamawa, Borno and Yobe.
The government announced a ceasefire with Boko Haram nearly two weeks ago as part of efforts to negotiate the release of more than 200 schoolgirls kidnapped by the group in April but there have been several abductions and attacks since then.
There are conflicting figures about the number of casualties in the Gombe bus bomb.
Witnesses at the scene and at Gombe hospital described seeing at least seven bodies.
It is not clear if Boko Haram is behind the attack but the militants have targeted commuters in the past.
Over the border in Adamawa, thousands of people have been fleeing Mubi since it came under attack on Wednesday.
The BBC Hausa Service spoke to one resident trapped in the town who said the fighters had set up checkpoints and that their intention was to impose Islamic law.
According to the resident, the militants said that several people who had been caught stealing motorbikes during the chaos of their takeover would have their hands cut off on Friday in front of the main mosque.