Unidentified gunmen ambushed a convoy of an oil servicing company in Nigeria's southern Rivers state and kidnapped two South Korean workers and killed four soldiers.

The convoy was attacked on Tuesday around the Ahoada/Abua axis, along the East-West road in the state.

The Koreans were among workers of Daewoo Engineering and Company - a South Korean firm - who were being escorted to work by the Nigerian soldiers.

Two drivers were also reportedly killed in the ambush.

The Nigerian army has since confirmed the killing of the soldiers and the abduction of the expatriates.

In a statement, Major Jonah Danjuma, an army spokesperson, said the military was tracking down the attackers to secure the two abducted workers.

The army blamed suspected militants for the attack but there was no immediate claim of responsibility.

Abductions for ransom are frequent across Nigeria.