Updated

Three Australians, two Nigerians, a New Zealander and a South African have been kidnapped in Nigeria in an ambush that killed their Nigerian driver, Australian officials said Thursday.

Authorities did not know who kidnapped the men, who were working for Australian mining contractor Macmahon Holdings, on Wednesday, Prime Minister Malcolm Turnbull said.

Turnbull said the Australian ambassador was on the scene and working with local authorities.

Another Australian had escaped during the ambush at Cross River State, Foreign Minister Julie Bishop said.

"We are treating this extremely seriously as, I understand, is the Nigerian government," Bishop told reporters.

"We have some understanding of what occurred," she said. "Suffice to say there are seven people currently being held."

Macmahon said in a statement that the dead driver and the seven kidnapped men were all employees. The kidnap happened near the city of Calabar.

"We are working to ensure the safe return of all the men involved and are in communication with their families," the statement said.