The Department of Foreign Affairs has confirmed it is investigating reports that an Irish man has been taken hostage aboard an oil rig in Nigeria.
A spokeswoman said lines of communication were very poor at the moment and details of the kidnapping were vague.
However, she confirmed that Irish consular staff in Lagos were assisting an Irish family.
Unidentified armed men captured four foreign oil workers - an American, a Briton, a Honduran and a Bulgarian - from Royal Dutch Shell's offshore EA oilfield yesterday.
The Irish man is understood to have been kidnapped in a separate incident today.
Violence against the oil sector is frequent in the Niger Delta, where an estimated 20 million people live in poverty alongside a multi-billion-dollar industry. Their resentment fuels killings, sabotage, kidnappings and massive oil theft.
Foreign oil workers kidnapped in Nigeria are almost always released after payment of a ransom, although some companies have a policy of not paying up.
In yesterday's hostage-taking, gunmen stormed the field in three boats and opened fire, injuring one person, before abducting the four foreign workers.
An industry source said production from the field, located 15 miles (25 km) from the coast of the southern Niger Delta, was shut down and workers were evacuated.