MAIDUGURI/ABUJA - Gunmen threw bombs and opened fire on a cattle market in remote northeastern Nigeria, killing at least 60 people, a spokesman for Yobe state governor said, an attack whose motives remain unknown.

"The Yobe State Governor has visited the Potiskum cattle market where he was informed that 60 people had been killed in the attack, while 29 people are receiving treatment at the Hospital," Abdullahi Bego, spokesman for Governor Ibrahim Gaidam, told Reuters by telephone.

It was not clear who was behind the attack overnight on Wednesday in the town of Potiskum. The town has been an occasional target for militant Islamist sect Boko Haram but it also suffers occasional bouts of ethnic violence over land disputes.

There was no immediate claim of responsibility for the attack. A hospital nurse said he had counted 56 bodies at the Potiskum morgue.

"I am sure that the death toll could rise in view of the serious nature of injuries sustained," the nurse at Potiskum hospital, Babangida, said. "The Potiskum mortuary is made up of a room and a parlour and I counted the 56 in the parlour only. I didn't go into the inner room."

Police Commissioner Moses Namiri earlier said security forces had confirmed 34 killed and that Islamist sect Boko Haram was suspected to be behind the attack.

"Everybody knows the modus operandi of BH (Boko Haram): they threw explosives and used guns," he said. "The gunfire lasted for almost an hour."

Witness Mama Yusuf, a retired civil servant, said there were bodies on the ground, though he could not say how many.

"I saw dead bodies all around the place and the emergency services taking people to hospitals," he said.  

Boko Haram has been fighting a low-level insurgency for more than two years and has become the main security threat facing Africa's top oil producer, although it is far from any oil producing facilities.

It usually targets police or authority figures, and although civilians increasingly have borne the brunt of its attacks, they are normally targeted for being a perceived enemy of the group, such as Christians, not randomly killed.

Sometimes violence in Nigeria, especially in parts of the north or the volatile Middle Belt - where the largely Christian south and Muslim north meet - is driven by ethnic rivalry over land and resources that has little to do with the Boko Haram.

The sect, which wants to impose an Islamic state on Nigeria's mixed population of Muslims and Christians, has been blamed for hundreds of killings since its uprising against the government began in 2009.  

A spate of attacks in the past few days, including one against Christians in the north that killed 19 people on Sunday, have dampened hopes that tighter security had significantly reduced the sect's capability.  

Nigerian forces killed the suspected mastermind of Sunday's attack on Christian worshippers, in a raid in the main northern city of Kano on Tuesday that resulted in a gun battle lasting several hours.