There are fears that up to 2,000 people have been killed in a massacre in Nigeria carried out by the Islamist group Boko Haram.

Many of those killed are women and children and the elderly who were unable to escape as the attackers descended on the town of Baga on Wednesday.

The Sunni jihadist group attacked with rocket-propelled grenades and assault rifles, the Associated Press reports. There are reports of the attackers killing with indiscriminate firing and burning down buildings.

Fighting between the insurgents and government forces continues in the town on Friday.

Amnesty International have called the attack the “deadliest massacre” ever carried out by the group, and there are reports of hundreds of bodies strewn across the town.

“If reports that the town was largely razed to the ground and that hundreds or even as many as two thousand civilians were killed are true, this marks a disturbing and bloody escalation of Boko Haram’s ongoing onslaught against the civilian population,” said Daniel Eyre, Nigeria researcher for Amnesty International.

Amnesty International said Boko Haram have committed "war crimes and crimes against humanity."

“The human carnage perpetrated by Boko Haram terrorists in Baga was enormous,” Muhammad Abba Gava, a spokesman a defense group that fights Boko Haram, told the Associated Press.

The Council on Foreign Relations estimates that the Boko Haram insurgency killed more than 10,000 people in 2014.