The main militant group in Nigeria's oil-producing Niger Delta said on Sunday it had released around 19 local oil workers kidnapped more than two weeks ago but was still holding two Britons and one Ukrainian, reported reuters. "The Nigerian hostages rescued from pirates by the Movement for the Emancipation of the Niger Delta (MEND) have been released in Rivers state," MEND said in an e-mailed statement. "Due to the location where the expatriates were kept for their safety, they cannot be released at this time because of security concerns," the group said.