Three Australians and a New Zealander are among seven mine workers kidnapped from a worksite in Nigeria, Prime Minister Malcolm Turnbull has confirmed.
The workers are employed by Perth-based mining and engineering company Macmahon Holdings.
Mr Turnbull said the gunmen also shot dead one of the mining company's drivers during the attack near the capital of Cross River State, Calabar.
"We don't know at this stage the identity of the kidnappers and families in Australia are notified of course," he said.
"It is a very serious kidnapping, a very serious criminal assault, one person was killed and seven people have been kidnapped."
The New Zealander is a permanent resident of Australia.
Foreign Minister Julie Bishop said the Government was working hard with Nigerian authorities to secure the release of the Australians.
However, Ms Bishop said she would not provide further details given the sensitive nature of the case.
Nigerian police said earlier that three foreign nationals — two Australians and a South African — and two Nigerians had been kidnapped and their driver shot dead.
The hold-up happened in the Akpabuyo district about 7:00am (local time) on Wednesday.
An eyewitness reportedly said the men were bundled onto a waiting boat.
Nigerian police commissioner Jimoh Ozi-Obeh said the police were working with the Nigerian Navy to ensure all victims were released unharmed.
An escort vehicle carrying local police was unable to prevent the abduction.
The commissioner said no ransom demand had been received.
'Well organised' kidnapping
The convoy is believed to have been attacked by about 30 militants.
Militant group Boko Haram, which operates in the north-east of the country, is thought unlikely to be responsible for the kidnappings as they happened in the south.
"It is more likely to be a criminal gang that have taken these people to elicit some sort of ransom from the company," ABC Africa correspondent Martin Cuddihy said.
He said kidnapping was not uncommon in this region.
"This is a very wealthy part of Nigeria, but given the fact that the oil price has dropped considerably in the last couple of years, these criminal gangs have taken to abducting more foreign nationals in an effort to raise some money," he said.
"There simply hasn't been the same amount of wealth pouring into that part of the country as there has been in recent years."