Police in the northern Nigerian city of Kano said on Tuesday they had rescued an in-law of President Muhammadu Buhari from kidnappers, freeing him after an overnight gunfight with his abductors.

Special police operatives on Monday evening stormed a hideout on the outskirts of Kano, where Musa Umar had been held since he was captured on May 2.

After hours of gunfire, Umar was “rescued unhurt, arrests were made and arms and ammunitions recovered”, Kano police spokesperson Haruna Abdullahi said.

Umar, who is married to Buhari’s niece, was abducted in May by four gunmen and forced into a car outside his house in Daura, the president’s hometown.

A police officer familiar with the rescue operation said the kidnappers had demanded $11m ransom during phone negotiations monitored by security operatives.

Eleven members of the gang were arrested and one was killed in the shootout, said the source who asked not to be named.

Kidnapping for ransom is widespread in the oil-rich southern delta region, where criminal gangs seize expatriate oil workers and wealthy Nigerians in exchange for large payments.