Geneva - Northeastern Nigeria is close to famine with hundreds of thousands trapped without help, and must be declared a "top emergency" by the UN, said medical charity Doctors Without Borders on Wednesday.
The charity, known by its French acronym MSF, said the region devastated by Boko Haram's Islamist insurgency had between 500 000 and 800 000 people trapped in areas that cannot be reached by humanitarian workers.
A UN "top emergency" designation - which would put Nigeria on a list with Syria, Iraq and Yemen - would immediately mobilise more resources to a crisis that has not received nearly enough attention, MSF said.
Boko Haram attacks in the northeast have declined over the last year, but MSF's emergency programme manager Hugues Robert noted that aid workers were still limited in where they can go.
Some cities in the northeast, such as Banki and Bama, had gone up to 18 months without any humanitarian deliveries before aid agencies and the UN arrived in June.
"What was extremely shocking was the level of severe acute malnutrition," Robert said, adding that communities faced "close to a famine situation".
Many areas can only be accessed under escort from the Nigerian army, he told reporters in Geneva after returning from Borno state, the epicentre of the Boko Haram insurgency.
"We need the UN and all their agencies to consider this as a top emergency," Bruno Jochum, director of MSF Switzerland, told reporters.
Boko Haram, which seeks to impose strict Islamic law in northern Nigeria, has been blamed for about 20 000 deaths and displacing more than 2.6 million people since 2009.