At least 98 people are still missing in addition to 160 confirmed dead a week after floods ripped through a town in central Nigeria, the national emergency agency said on Wednesday, as hopes of finding survivors fade.

Heavy rainfall unleashed waters that destroyed homes and overwhelmed local drainage systems in Mokwa, about 270 kilometres (168 miles) west of Abuja, in one of the deadliest floods to hit Africa's most populous country.

Although search and rescue operations continue, damage to roads and bridges was hampering access, said the National Emergency Management Authority (NEMA), which has enlisted the help of Nigeria Red Cross, police and army.

"Teams are working to locate missing persons. There is heightened risk of disease outbreaks due to overcrowding and contaminated water sources," NEMA said in a statement.

Woman's four children swept by floods

Habiba Abdulahi, a 27-year-old resident, said four of her five children had been washed away by the floods, and that like other victims' relatives she was still hoping that the bodies would be found.

"Just like that, my children were gone. Even now, we haven't found them, but we are still hoping to recover their bodies," she told Reuters by phone.

The United Nations Children's Fund in Nigeria said it had deployed a team to provide essential healthcare services, including to pregnant women.

Nigeria frequently experiences floods during the rainy season, which typically begins in April and ends in October.