YAOUNDE - At least 15 people have been killed in an attack by suspected Boko Haram militants on a bus in northern Cameroon, a senior local security official and a businessman said on Saturday.

Over the last year, Boko Haram , which has killed thousands in its struggle to create a caliphate in northern Nigeria, has stepped up attacks on both sides of the border, forcing Cameroon to dispatch thousands of troops to its north.

‘Boko Haram elements on Thursday attacked a bus that was transporting many passengers from Kousseri to Maroua and killed 25 persons on the spot,’ said a senior officer in the military’s BIR rapid reaction unit deployed in the region. The officer, who asked not to be named, said another 10 people had been severely injured and taken to Maroua hospital and he feared the death toll would rise.

Maroua is the capital of the Far North region, which has seen the worst of the spillover of Nigeria’s conflict. Cameroonian authorities were not available for comment on the attack, which took place in the evening of Jan. 1. However, a local businessman based in the north said travellers who reached the town of Maroua had confirmed the incident.

Foncha Ngeh, who is based in Maroua, said travellers had told him there were at least 15 dead in the incident but many more had been injured and were being transported to Maroua for treatment. Ngeh said there had been a string of other attacks in the region, carried out by Islamists but also ordinary bandits targeting people travelling during the holidays with lots of cash. Late last month, Cameroon had to call on its air force to help troops dislodge Boko Haram fighters who briefly occupied a military camp after hundreds of militants mounted a wave of attacks on five northern towns. Raids by Boko Haram have forced many Cameroonians living along the porous border to abandon farms, raising the risk of food shortages in the semi-arid part of the country.

Moreover, Gunmen abducted 40 boys and young men from a remote village in northeast Nigeria in a raid that residents and a security source blamed on Boko Haram , the Islamist group that has gained worldwide notoriety for mass kidnappings. Witness Mohammed Zarami said the gunmen arrived at the village of Malari around 8 p.m. on Wednesday, heavily armed but did not fire shots or kill anyone.

‘People ran out of their houses in fear but they warned no one should disobey them,’ Zarami told Reuters in the northeast city of Maiduguri, where he had fled to on foot. ‘They took away over 40 (male) youths mostly between the ages of 15 to 23. As I am talking to you now, there is no youth in our village,’ he said. Boko Haram fighters have abducted hundreds of people in the past year. Boys are recruited as fighters and the girls as sex slaves, security officials say.

Its five-year-old uprising for an Islamic state is the gravest security threat to Africa’s top economy. Parents of 200 Nigerian schoolgirls kidnapped by Islamist rebels in April have said they are appealing to the United Nations for help after losing hope that the Nigerian government would rescue them. A man claiming to be Boko Haram leader Abubakar Shekau at the end of October said in a video that the girls had been ‘married off’ to Boko Haram commanders.