Dozens of people are missing feared dead in north-western Nigeria after a boat carrying about 200 broke in two and sank in a river, officials say.

Most passengers were women and children travelling from Niger state to neighbouring Kebbi state.

At least 20 people have been reportedly rescued, with the authorities blaming Wednesday's accident on overloading.

Divers and emergency workers were trying to save others in the Niger River, local officials told the BBC.

President Muhammadu Buhari described the accident as "devastating", offering his condolences to the victims' families.

"Only 20 people have been rescued alive, four dead confirmed while the remaining 156 people are still missing and they are believed to be underwater," National Inland Waterways Authority local manager Yusuf Birma was quoted as saying by the AFP news agency.

Abdullahi Buhari Wara, administrative head of Ngaski district, told the AFP news agency that he blamed the accident on overloading. The boat was also loaded with bags of sand from a gold mine, he said.

Qasimu Umar Wara, a resident of the nearby town of Wara, earlier said that five bodies had been recovered but many more are expected to wash up in the days ahead.

The boat was overloaded, he said: "My brother is among those missing. This is the worst boat accident that has happened in this water."

Boat accidents along the River Niger are common with overcrowding a major cause, as well as collisions with tree trunks under the water.