A first class traditional ruler in Nigeria's Ondo state was killed by gunmen while returning to his palace on Thursday evening.

Oba Adegoke Adeusi's official vehicle was shot at while being driven on the highway and he sustained serious wounds.

He died on arrival at the Federal Medical Centre in Owo area, local media report.

Oba Adegoke's relatives told local media the attack was staged like an assassination as nothing was stolen from his vehicle.

The monarch was on his way from a council meeting when the attack took place.

There have been several incidents of kidnappings and killings on the highway.