Nigeria's most active militant group has claimed responsibility for the kidnapping of a Canadian oil worker and six of his colleagues after an attack on an oil rig off Nigeria on Monday.

"All the abducted expatriates are well and in our safe custody," the Movement for the Emancipation of the Niger Delta (MEND) said in an emailed statement to Reuters.

The group said it would soon release the names of all the hostages being held, although according to Newfoundland television station NTV, the Canadian has been identified as Robert Croke, a resident of St. John's.

Croke and the others, identified as two Americans, two French nationals and two Indonesians, were on the oil rig High Island VII, which had recently arrived at an oilfield, some 12 kilometres off the coast off Akwa Ibom state.

"I can confirm one hostage is Canadian," Postmedia News was told by James Henderson of Pelham Bell Pottinger, a public relations company for Afren, the United Kingdom-based company that operates the rig.

NTV News said Croke, 51, works for PPI Technology Services, a drilling management company based in Houston.

Canada's Department of Foreign Affairs said in a statement it is aware of reports that a Canadian national is missing and presumed kidnapped in Nigeria.

"The Department of Foreign Affairs and International Trade is in touch with local authorities with a view to seeking further information. Due to the Privacy Act, no additional information can be released at this time," said spokeswoman Lisa Monette.

In addition to the hostages, an Afren statement said: "Two crew members are stable after receiving wounds to the leg, and have been evacuated by helicopter to a shore-based clinic."

The pre-dawn attack happened in the country's turbulent Niger Delta region, the heart of one of the world's largest oil industries.

Most kidnappings in the region are for ransom, but no demands had been made yet.

The militant group said on Monday it was also holding one Thai and three French nationals who were kidnapped several weeks ago and had since been transferred to its custody.

The three Frenchmen were kidnapped from a vessel owned by French marine services company Bourbon on Sept. 22 by gunmen in speedboats.

Meanwhile, Afren said in its statement that a second "security breach" happened at a support vessel, but did not provide details. The statement said "the vessel and rig are both under the control of the company."

Preparations for drilling operations on the rig had been temporarily suspended.

Afren is headquartered in Britain and works with a local partner, AMNI International, while the rig is owned by Transocean.

Nigerian security officials could not provide precise details on the attack, one of the latest in the Niger Delta.

Criminal gangs seeking ransom payments as well as militants claiming to be fighting for a fairer distribution of oil revenue have abducted scores of foreigners and family members of wealthy Nigerians in recent years.

An amnesty deal offered to militants last year greatly reduced unrest in the Niger Delta, but several incidents have occurred in recent months ahead of elections set to take place early next year.

Sabotage of oil facilities occur frequently in the region. Late last month, a pipeline belonging to the Italian oil firm Eni was attacked, causing a 4,000-barrel-per-day production cut.

Nigeria is one of the world's largest oil exporters.

- With files from Reuters and AFP