"Our men have been through a traumatic experience, and we have mobilised medical and other support teams in Nigeria to provide immediate support," he said.
"I also thank the men's families for working so closely with the company during what has been an extremely difficult time for them as well. They too have endured an incredibly stressful experience."
He said the families had been told of the release and had spoken to their loved ones.
According to The Guardian Nigeria a state security adviser said the seven men were unharmed after their ordeal.
"They are safe and sound," said Jude Ngajim.
All men had been seen by a doctor and seven were "fit and sound".
New Zealand Ministry of Foreign and Affairs and Trade this morning confirmed the workers held captive for four days were now free.
"We are pleased to confirm the advice from Macmahon Holdings that its seven workers, including a New Zealander, have been released safely.
"We are in close contact with the New Zealander's next of kin who have been informed of the successful release."
She said the ministry would not be providing any comment on the circumstances surrounding the release of the group, or their current situation.
A Nigerian driver was shot dead in the attack, while the kidnapped men also included a South African and two Nigerians.
Another Australian managed to flee the attackers.
Macmahon Holdings mines material for processing at Lafarge Africa's UniCems cement plant at Mfamosing, in Nigeria's southeast.
The company didn't say if a ransom was paid for the men's release.
Foreign Minister Julie Bishop last week stressed Australia had a long-standing bipartisan policy of not paying ransoms on demand from kidnappers because to do so would increase security issues for travellers.
Mr van Dyk praised the efforts of Nigerian authorities, saying they worked closely with the company.
"We are very grateful for the professional support we have received from the authorities on the ground in Nigeria," he said.
He also praised Australian, New Zealand and South African authorities and the company's security advisors who supported Macmahon's crisis management team.
"This has been an incredible team effort and our highest priority now is to finish the job by continuing to work together to get our people back safely to their families and homes," he said.
"While we understand the media's interest in these developments we ask that the privacy of all the families be respected at this time."
-AAP
