A ferry has reportedly been hijacked in Nigeria.

The unidentified vessel left Port Harcourt on Tuesday at 7am local time (0600 GMT) carrying 11 passengers. It went missing shortly thereafter, security provider Diaplous Maritime Services said.

"Local maritime authorities have reported that the vessel was hijacked by unknown gunmen," Diaplous' alert said.

The whereabouts of passengers and crew member are unknown, and the exact time and location of the hijacking have not yet been determined, the company said.