Four more foreign oil workers have been kidnapped from a supply vessel in southern Nigeria's Niger Delta region.
The kidnapping of two Norwegians and two Ukranians is the latest in a string of assaults on foreign contractors.
The rise in attacks by militants has reduced Nigerian oil production by 25%. Militants demand more local control of the Delta's rich oil resources.
Kidnappings have also been used to extort money from oil companies and from the government.
Shipping company Trico Marine Services TRMA.O confirmed four workers were kidnapped on Wednesday.
"We will not come out with more information than that four of our crew were taken from a ship off Nigeria," managing director Bjoern Endresen told Reuters news agency.
He said no demands had been made.
The Norwegian government confirmed the men had been kidnapped, AFP news agency reports.
Last week, three Filipinos and one German were kidnapped in the region.