The Nigerian army and navy spokesmen said they had no information about the incident, while a spokesman for the joint armed forces unit that is in charge of security in Rivers could not be reached.
It was not clear if the kidnapping was the work of ransom-seekers or of rebels seeking to press political demands. Okrika is a stronghold of a well-known local militia, but there was no immediate claim of responsibility.
Abductions, mostly for ransom, are common in the Niger Delta, where residents live in poverty alongside Africa's biggest oil industry.
Five Chinese telecom workers were kidnapped in a different part of Rivers on Friday and are still missing.
Separately, the rebel Movement for the Emancipation of the Niger Delta is still holding captive three Italians and one Lebanese employed by Italian oil company Agip who were kidnapped on December 7.
The group, which wants local control of oil assets and reparations to communities for pollution and neglect, said it was not involved in Sunday's attack.