By Kieran Guilbert

DAKAR (Thomson Reuters Foundation) - Ravaged by years of Boko Haram violence, pockets of northeast Nigeria controlled by the Islamist militant group and cut off from aid could be facing famine, food analysts said on Friday.

Around three million people in the northeast have been identified as urgently needing food and other humanitarian aid, but the situation could be far more severe, according to the U.S.-based Famine Early Warning Systems Network (FEWS NET).

"We are concerned about small pockets where the situation may be much more dire," said Bruce Isaacson of FEWS NET, which is run by the U.S. Agency for International Development (USAID).

"There could be famine in some of the worst affected and most isolated areas," he said, adding that it was difficult to judge the level of hunger due to a lack of access and data.

A regional offensive last year drove Boko Haram from much of the territory it held in northern Nigeria, undermining its seven-year campaign to carve out an Islamist caliphate.

But the militants have since struck back with suicide bombings and hit and run attacks on civilians.

The violence, which has killed more than 15,000 people and uprooted 2.4 million in Nigeria, Chad, Niger and Cameroon, has pushed food insecurity and malnutrition to emergency levels in northeast Nigeria, according to the Nigerian government.

People are struggling to obtain food due to a lack of humanitarian access, disruption to markets and agriculture, and rising prices caused by the naira's depreciation, FEWS NET said.

Improving security has enabled aid agencies in recent months to reach areas that were previously cut off, but many remain unreachable due to the ongoing violence and lack of security.

"Even if there is not a full famine situation in those areas, it's clear the situation is extremely dramatic," said Luca Russo of the U.N. Food and Agriculture Organization (FAO).

"People are already in a situation which is very difficult to reverse in terms of degradation of livelihoods and nutrition," Russo told the Thomson Reuters Foundation.

Tens of thousands of children in northeast Nigeria will die of malnutrition this year unless they receive treatment soon, the U.N. children's agency UNICEF said last week.

The U.N. World Food Programme (WFP) in May announced it would provide food aid to more than 400,000 people to avert the threat of famine as the lean season approaches.

(Reporting By Kieran Guilbert, Additional Reporting by Magdalena Mis in Rome, Editing by Ros Russell; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit news.trust.org)