The Foreign Office later confirmed that two of the men were engineers, David Welsh, 63, who is resident in Spain, and Keith Miller, 50, who is understood to be from the Newark area of Nottinghamshire. The men, who are employees of Niger-Benue Transport Company, were seized on Monday outside the firm's premises in East Warri.
Mr Miller's sister-in-law, Kathleen Peart, from Lincoln, said: "We are placing our hope and confidence in the company that it will undertake successful negotiations on behalf of our family."
Two other British men were seized during a ship hijack in the Niger delta on 6 August. Another four British men kidnapped in this incident were released in Port Harcourt. A spokesman for the Foreign Office said that some of the kidnapped men were oil-company workers, and that this was the latest in a series of abductions of foreign and British nationals in the area.
Last month a Briton and an Australian working in Nigeria for Royal Dutch Shell were released three weeks after they were taken hostage with their helicopter in the Delta region.
Resentment against the multinational energy firms has been a long-running feature of the oil-rich West African country, where many locals complain that few profits reach ordinary people.
The Foreign Office warns Britons working in the oil and gas industry that they run the risk of being held captive, either by protesters or even their own colleagues, during industrial disputes. There have been a number of similar incidents this year, although all the Britons involved were set free unharmed.Reuse content