Nigerian troops have been accused of indiscriminate shootings and other abuses in a troubled town where gunmen this month massacred 40 people, including students, a lawyers' group said Thursday.

Some residents of Mubi, a commercial hub and university town in northeast Nigeria's Adamawa state near the border with Cameroon, also said soldiers deployed to find the killers have resorted to abuses.

The military has denied the accusations, which came after hundreds of soldiers deployed to the town over a massacre overnight October 1 to 2 that saw gunmen open fire in a student housing area.

"Since their deployment, soldiers have been brutalising residents, shooting them at random and vandalising their vehicles at will," Sani Shehu Mohammed, head of the lawyers union in Mubi, told AFP.

"They drive on high speed in the town in total disregard to traffic laws and use cudgels to smash the windshields of vehicles that stand in their way."

Soldiers shot and injured at least three people Wednesday when they opened fire outside a market in the town following an explosion targeting a passing military vehicle, residents said.

"An explosive went off, missing its target, a passing military van, outside the Kuturu market and soldiers in the van came out and fired into the crowded market, injuring three people," one resident said.

Mohammed accused soldiers of shooting to death a terrified motorist on Monday as he struggled to park by the roadside to give way to a speeding military van close to the scene of the student massacre.

"Soldiers jumped out of their van and opened fire on the motorist, killing him on the spot," Mohammed said, adding that lawyers in the town were considering court action over the allegations.

Brigadier General John Nwaogu, head of the army in Adamawa state, strongly denied the accusations.

"It is not true. We have never molested anybody," he told AFP. "We conduct our operations based on intelligence information and we are there to protect the people in the first place."

Troops deployed to combat Boko Haram Islamists in northeastern Nigeria have often been accused of scorched-earth tactics, including extrajudicial killings and the burning of homes in areas where they are attacked by the extremists.

Last week, Human Rights Watch said Nigerian security forces as well as Boko Haram may both be guilty of crimes against humanity over violence that has killed more than 2,800 people since 2009.

Authorities have not said who was behind the massacre in Mubi.

The killings came days after a high-profile military raid targeting suspected Boko Haram hideouts, but some have suggested a student election dispute may have been behind the attack.