New Zealand's cybersecurity watchdog is urging anyone who receives an email bomb threat to contact the police immediately.
Cert NZ says it is aware of a campaign of blackmail emails threatening bombs, both internationally and in New Zealand.
The suspicious emails claim an explosive device has been planted in the recipient's office and will be set off unless a ransom is paid in the currency bitcoin.
CERT says while it is likely to be an opportunistic scam, the police are treating the emails as real threats until confirmed otherwise.
The agency says anyone receiving such an email should call 111 immediately.
It advises recipients not to respond or try to contact the sender and not to pay the ransom or take any other action before speaking to the police.
CERT says the threatening email should be kept as evidence for any police investigation.