Anti-riot policemen patrol the streets of Jos, in central Nigeria. Picture: AFP

The workers, two of whom later escaped, were contractors for cement company Lafarge Africa.

Local news source Punch Nigeria reported six men were taken in total and named them as “Jack Countentz (Australia); Mark Gabberdy (Australia); Peter Zoutenbier (Australia), Wayne Smith (South Africa), Jamal Khan (New Zealand), Austin Enok (Nigeria) and a driver simply identified as Howel (Nigeria).”

No official statement has yet been made as to their identities. The families have been notified

Prime Minister Malcolm Turnbull has told media the situation calls for restraint:

“The less Julie (Bishop) and I say about this the better from the point of view of recovering the kidnapped

“It is a very serious kidnapping, a very serious criminal assault”

Mr Turnbull said three Australians and one permanent Australian resident (who is a New Zealand national) were believed to be among the kidnapped. He said there were two Nigerian locals, with a seventh person believed to be from South Africa.

Ms Bishop later added that a fifth Australian had been able to evade the kidnap.

They were attacked on the outskirts of the city of Calabar at about 5.30am on Wednesday local time (2:30pm AEST), police said. Two of the trio managed to flee, Irene Ugbo, a spokeswoman for Cross River state police, adding she did not know the nationality of the workers still being held.

The kidnappers had yet to contact police, she said.

Lafarge Africa said it had been informed of the incident by Australian contractor Macmahon.

“Macmahon is working with the security agencies to resolve this situation,” said Viola Graham-Douglas, a spokeswoman for Lafarge Africa.

Macmahon could not immediately be reached for comment.

Mining services company MacMahon Holdings has put its shares in a trading halt ahead of an announcement relating to the kidnapping of its contract workers.

MacMahon requested the halt “pending an announcement about a security incident at an operation in Africa”