A bombing at a bus station in northeast Nigeria killed at least 20 people on Monday, as Boko Haram was blamed for a separate attack in the embattled region.
Violence in the northeast is escalating ahead of Nigeria's February 14 general elections, with many concerned that voting will be impossible in large parts of the region.
The blast hit the Dukku motor park on the outskirts of Gombe city, capital of Gombe state, at roughly 10.50am (local time), officials said.
State secretary for the Red Cross Abubakar Yakubu Gombe said his staff sent 20 body bags to the scene and "they have all been exhausted".
"We are still looking for more bodies among the carnage," he told AFP, adding that another 18 people with "serious" injuries had been taken to hospital.
The attack happened as reports emerged that Boko Haram militants had torched the town of Geidam in neighbouring Yobe state at the weekend.
The bomb in Gombe was planted near a bus that was filling up with passengers, said Mato Yakubu of the National Orientation Agency, a government body responsible for the media.
The city was hit by a triple bombing blamed on the Islamists on October 31.
Witness Awwalu Lame said a mob formed at the station shortly after the blast went off, with locals throwing stones at the security services.
Anger has risen across northern Nigeria amid complaints that the security services have repeatedly failed to contain the violence.
Boko Haram gunmen stormed Geidam in Yobe on Sunday, setting fire to several buildings and forcing residents to flee to the bush, witnesses said.
"They were chanting Allahu Akbar and firing shots and throwing bombs. We spent a night in the bush but from afar we could see in the darkness flames and smoke coming from the town," said resident Adamu Shehu.
Geidam in the hometown of Yobe's governor Ibrahim Geidam and his home was also razed, witnesses said.
"Our town is a mess," said resident Brema Umar, who reported that scores of people had fled overnight, many towards Yobe's capital Damaturu.
President Goodluck Jonathan, who is running for a second term, has on several occasions claimed that Boko Haram's defeat was imminent, even as the violence has escalated.
The insurgency has forced more than 1.5 million people from their homes, straining resources in the embattled northeast, as communities struggle to care for those displaced.
Underscoring the severity of the crisis, 185 people, mostly women and children, were kidnapped on December 14 from the town of Gumsuri in Borno.
The attack recalled the kidnapping of more than 200 schoolgirls from a school in the town of Chibok in April, a mass abduction that Jonathan vowed would not happen again.