Four Italians, an American and a Croat, working for Chevron, were kidnapped May 1. Militants said they would not demand any money, and that that the hostages would be released in a month's time if Bayelsa state authorities did not offer any ransom money.
"We will release them unconditionally May 30," the representative of the Movement for the Emancipation of the Niger Delta said in a letter to Italy's Agr news agency.
"Any offer of money will be considered an insult and will aggravate the hostages' position," they said.
"We will continue our struggle until we reach our goals," the representative said.
Nigerian rebels, who demand a larger quota from the government during distribution of revenue from oil production, often abduct oil workers, and mostly release them for a cash ransom.
A Belarusian woman, who is married to a Nigerian and is a senior manager with the local branch of the British services company Compass Group, was kidnapped Saturday night while returning from work in the country's main oil city of Port Harcourt. Gunmen stopped her car and took the woman away.
The latest kidnapping has brought the total number of foreign workers abducted in Nigeria to 28 in a week. Eight hostages have already been released.
