An American was one of six foreign oil workers taken hostage last night by a Nigerian militant group in an attack on a Chevron facility. At 5 a.m. local time, the attackers forced their way onto a storage and off-loading vessel and kidnapped six employees, the American, a Croatian and four Italians, according to Chevron. Chevron also said Government Security Forces may have suffered casualties during the attack. The militant group MEND (Movement for the Emancipation of the Niger Delta) claimed responsibility for the attack. In an e-mail to ABC News, the group’s self-proclaimed leader, who goes by the name of Jomo, warned that this attack should be seen as a "warning to the incoming government which we view as an extension of the present." Nigeria held elections for the first time last month, but many claim that the ruling party’s huge victory was due to fraud. The e-mail claimed that the hostages would be "released unconditionally" at the end of the month only if there are no offers of ransom made by the oil companies. Today’s kidnappings are the latest in a slew of attacks on oil workers and facilities in the Niger Delta.