Devastating floods collapsed walls at a jail in Maiduguri in northeastern Nigeria early last week, allowing 281 prisoners to escape, prison authorities said on Sunday.

Seven of the escaped inmates have been recaptured in operations by security agencies, Umar Abubakar, spokesperson for the Nigeria Correctional Services said in a statement.

"The floods brought down the walls of the correctional facilities including the Medium Security Custodial Centre, as well as the staff quarters in the city," Abubakar said.

Operations to recapture the remainder of the inmates were underway, he said.

Maiduguri is the capital of Borno state which early last week suffered its worst floods in decades. The flooding began when a dam overflowed following heavy rains, decimating a state-owned zoo and washing crocodiles and snakes into flooded communities.

The flood has killed at least 30 people according to the country's emergency agency and affected a million others, with hundreds of thousands of people forced into camps for displaced people.