Boko Haram has attacked the north-eastern Nigerian city of Maiduguri with explosions and a suicide bombing that witnesses said killed as many as 20 people.

The attack began in the early hours of Tuesday morning when residents were woken by explosions, heavy gunfire and the screech of a fighter jet scrambling to protect the area.

“We are under siege,” Sumaila Ayuba, her voice shaking, told the Associated Press by telephone just after midnight from her home on the city’s western edge. “The shooting is quite deafening. Please, we need prayers.”

Hours later, a man blew himself up at Gamboru cattle market, according to witnesses who spoke on condition of anonymity for fear of reprisals. One said he counted at least 20 bodies.

More than 30 people died in attacks over the weekend.

Boko Haram’s six-year-old uprising aimed at imposing sharia law across Nigeria has killed 13,000 people and driven 1.5 million from their homes.

President Muhammadu Buhari announced at his inauguration on Friday that he was moving the military headquarters of the war from Abuja, the capital in central Nigeria, to Maiduguri. The capital of Borno state is also the birthplace of the extremist Islamist group and the biggest city in north-eastern Nigeria.

Buhari, a retired major general who was briefly a military dictator in the 1980s, was set to hold his first meeting with military chiefs on Tuesday, amid speculation that there will be changes in the war against Boko Haram.

On Wednesday he will travel to Chad and Niger, whose troops help fight Boko Haram, said his spokesman, Garba Shehu. It is Buhari’s first official trip outside Nigeria. Chad and Niger complained of a lack of cooperation with the previous administration.

Hit-and-run attacks on villages and bombings are continuing, weeks after the military announced that a multinational offensive had forced Boko Haram from the towns and villages where it had declared an Islamic caliphate.