ABUJA (REUTERS) - Nigeria's presidency said on Tuesday the World Bank had pledged to spend up to US$2.1 billion (S$2.8 billion) to rebuild the north-east of the country that has been devastated by Boko Haram militants.

President Muhammadu Buhari met with representatives of the World Bank, the Bill and Melinda Gates Foundation, and the World Health Organisation during a trip to Washington.

A World Bank spokeswoman said that during the meeting, the bank said the sum of US$2.1 billion could be lent to Nigeria from its development agency and that support could also come from the International Bank for Reconstruction and Development.

"Apart from rebuilding the region in terms of infrastructure, priority must also be given to the resettlement of internally displaced persons, who now number over one million," Buhari was quoted as saying in government statement.

The loan would be spent through the World Bank's International Development Agency and would be interest-free for the first 10 years.

The statement said the World Health Organisation would spend US$300 million on immunisation against malaria, while the Bill and Melinda Gates Foundation would work with Nigeria's Dangote Foundation to maintain the record of zero polio cases for the past year.

Buhari met US President Barack Obama on Monday to discuss how to tackle the insurgency in his first visit to Washington since his election in March.

The Islamist Boko Haram has been waging a six-year-old insurgency with the aim of carving out a caliphate in the north of Nigeria, Africa's biggest economy.