Two suicide bombers blew themselves up in the main police station of north Nigeria's Potiskum in Yobe state on Saturday, witnesses said, in another apparent attack by Boko Haram jihadists.

A death toll was not immediately available.

Earlier Saturday, a bomb strapped to a girl aged about 10 exploded in a busy market place in the northeastern city of Maiduguri, killing at least 16 people and wounding more than 20, security sources said.

Yobe state is one of three northeastern states frequently attacked by Sunni jihadist group Boko Haram, which is trying to carve out an Islamic state. Maiduguri, the capital of Borno state, lies in the heartland of the Boko Haram insurgency and is often hit by bomb attacks.

On Friday evening, the army repelled an attack by insurgents in Yobe state capital Damaturu.

However, hundreds of bodies — too many to count — remained strewn in the bush near Baga following an attack that Amnesty International suggested Friday is the "deadliest massacre" in the jihadist group's history.

Armed forces finally drove of the insurgents who attacked Baga, a town on the border with Chad where insurgents seized a key military base on Jan. 3 and attacked again on Wednesday.

"Security forces have responded rapidly, and have deployed significant military assets and conducted airstrikes against militant targets," Mike Omeri, the government spokesman on the insurgency, said in a statement.

District head Baba Abba Hassan said most victims are children, women and elderly people who could not run fast enough when insurgents drove into Baga, firing rocket-propelled grenades and assault rifles on town residents.

"The human carnage perpetrated by Boko Haram terrorists in Baga was enormous," Muhammad Abba Gava, a spokesman for poorly armed civilians in a defence group that fights Boko Haram, told The Associated Press.

Boko Haram Baga killings attack

Baga, a town on the border with Chad, has been targeted by Boko Haram multiple times in recent years. (Google/CBC)

He said the civilian fighters gave up on trying to count all the bodies. "No one could attend to the corpses and even the seriously injured ones who may have died by now," Gava said.

Omeri said the National Emergency Management Agency, working with the Red Cross, was providing humanitarian assistance to 2,000 people who had fled Baga.

An estimated 2,000 more people crossed the border to Chad over the last week, prompting the country to call for international aid. Cameroon has also appealed for aid to help fight the militants.

As many as 2,000 killed

An Amnesty International statement said there are reports the town was razed and as many as 2,000 people killed.

If true, "this marks a disturbing and bloody escalation of Boko Haram's ongoing onslaught," said Daniel Eyre, Nigeria researcher for Amnesty International.

Nigeria Violence

A young girl stands amid the burned ruins of Baga, Nigeria, following an attack in April, 2013. The jihadists behind that attack struck again on Friday in what Amnesty International has called the "deadliest massacre" in the history of Boko Haram. (Haruna Umar/Associated Press)

The previous bloodiest day in the uprising involved soldiers gunning down unarmed detainees freed in a March 14, 2014, attack on Giwa military barracks in Maiduguri city. Amnesty said then that satellite imagery indicated more than 600 people were killed that day.

The five-year insurgency killed more than 10,000 people last year alone, according to the Washington-based Council on Foreign Relations. More than a million people are displaced inside Nigeria and hundreds of thousands have fled across its borders into Chad, Cameroon and Niger.

'I saw them kill my father'

Emergency workers said this week they are having a hard time coping with scores of children separated from their parents in the chaos of Boko Haram's increasingly frequent and deadly attacks.

Boko Haram Vigilantes

Nigerian traditional hunters have formed groups, commonly called the Vigilantes, that use locally-made weapons to help government forces combat Boko Haram in the rural northeastern regions of the country. (EPA)

Just seven children have been reunited with parents in Yola, capital of Adamawa state, where about 140 others have no idea if their families are alive or dead, said Sa'ad Bello, the co-ordinator of five refugee camps in Yola.

He said he was optimistic that more reunions will come as residents return to towns that the military has retaken from extremists in recent weeks.

Suleiman Dauda, 12, said he ran into the bushes with neighbours when extremists attacked his village, Askira Uba, near Yola last year.

"I saw them kill my father, they slaughtered him like a ram. And up until now I don't know where my mother is," he told The Associated Press at Daware refugee camp in Yola.

With files from The Associated Press