Lagos - A bombing at a bus station in Gombe city in northeast Nigeria killed at least 20 people on Monday, the latest violence in the region repeatedly targeted by Boko Haram, the Red Cross said. Nigeria is set to hold a general election on 14 February, but relentless bloodshed has raised security concerns ahead of the poll, with some warning that voting may be impossible in large parts of the northeast. "There was an explosion at the Dukku motor park. The Red Cross mobilised with 20 body bags and they have all been exhausted," said Abubakar Yakubu Gombe, area secretary for the Red Cross. "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 bomb 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. He said the blast occurred at 10:50 (09:50 GMT) at the station on the outskirts of Gombe city, capital of Gombe state. The city was hit by a triple bombing blamed on the Islamists on 31 October. The state shares a border with Borno and Yobe, two of the states worst affected by Boko Haram's five-year insurgency which has cost more than 13 000 lives. The Islamists have claimed a number of attacks at bus stations, often targeting people who are heading to Nigeria's mainly Christian south. 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 following complaints that the security services have repeatedly failed to contain the violence. While experts agree that isolated bombings are extremely difficult to stop, the broader military response to the extremist uprising has been widely criticised. 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 14 December 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. The president's opponent in February polls, ex-military dictator Muhammadu Buhari from the mainly Muslim north, is seen by some as better placed to contain the Boko Haram threat, but experts say he may struggle to unseat an incumbent with the backing of a wealthy ruling party.