Boko Haram terrorists have stepped up attacks on vulnerable people including those living in camps in northeastern Nigeria pushing the displaced from "one hell into another," a leading international aid agency says.

The Norwegian Refugee Council (NRC) said on Friday that the terrorists were looking for softer targets, including camps hosting the displaced, following the intensification of offensive by the Nigerian military against the militants.

Latest data from the NRC showed that civilians were affected by violence on about 200 occasions last month – three times more than the total for June.

It also indicated that at least 32 attacks were carried out on camps and sites for those uprooted by the conflict since July.

“Camps sheltering innocent families fleeing war should be places of refuge but instead they are turning into death traps,” the head of programs for NRC in Nigeria, Ernest Mutanga, said in a statement.

“Armed groups in this conflict are pushing people from one hell into another,” he added.

Terrorists have killed and injured dozens of civilians in recent months in a spate of attacks on camps and areas sheltering the displaced that bore the hallmarks of Boko Haram.

Eight years of militancy by Boko Haram has so far killed more than 20,000 people and forced more than 2.7 million to flee their homes.

Last year, the Nigerian army seized large swathes of territory from the terrorists; however, the militants have struck back with renewed zeal since June and killed at least 170 people and weakened the army's control in the northeast.

Many aid agencies, including the NRC, have been forced to temporarily suspend their aid work in Maidiguri, the capital of Borno state, due to threats from Boko Haram.

“We are worried that if these attacks continue, a very bad situation will grow even worse when it comes to aid access and delivery," Jackie Okao, protection and advocacy adviser at the NRC in Nigeria, told the Thomson Reuters Foundation by phone.

The United Nations' World Food Program (WFP) says about 5.2 million people are expected to need food aid by the end of this month - an increase of 500,000 from the start of 2017 - in a region threatened with famine.

According to aid agencies, the situation could be far worse with many areas cut off from help due to the threat of Boko Haram and the arrival of the rainy season restricting access.