Police are warning the public to think before sharing personal details online after a Canterbury person was scammed out of $320,000 in life savings.

The scam involved investments in cryptocurrencies, such as bitcoin, and the company involved offered good returns for minimal investment.

The investment grew as more money was deposited, but soon began to decline, Senior Sergeant Paul Reeves said.

The scammer then contacted the victim on numerous occasions to invest more funds, which they deposited via the website.

"Members of the public should seek advice before making any online investments they are unsure of.

"Scammers are extremely persistent and can seem very credible, as they are highly versed in their trade," Reeves said.

Anyone who believed they had been a victim of a crime, in person or online, should report the matter to their local police.

According to experts Kiwis are losing up to $500 million annually to international scammers and the number of reported incidents has risen sharply this year.

Experts say the money is putting a dent in the New Zealand economy with many scams driven by organised crime groups and overseas cartels.

Earlier this year, A Herald investigation revealed details about the level of scamming activity in this country, the growing cost to victims and the psychological harm inflicted by the criminals who perpetrate these scams from around the globe.

Cases include:

• A couple whose son borrowed more than $2m from them and lost it all investing in binary options. Such scams are now being presented as cryptocurrency investments online.

• A father who chipped away $800,000 in an inheritance scam in the hope he would eventually inherit $2m to help his children buy their own homes.

• An elderly woman tricked out of nearly $567,000 in a romance scam by a man she believed was her true love. He claimed he needed money to oversee the completion of a hospital in Ghana for a friend whose family had been killed in a car crash. The scam was only detected by the woman's broker when she tried to borrow $300,000 more to send overseas.

Bronwyn Groot, manager fraud education at the Commission for Financial Capability, has spent two decades in fraud investigation work for the banking sector but now advocates for scam victims.

Groot told the Herald there were three main categories of scams.

• Love and money: The victim sends money to a potential romantic partner. Commonly the scammer is someone they've never met who lives abroad.

• Something for nothing: The victim sends money to a stranger overseas but expects to eventually gain something in return such as a lottery win or inheritance.

• Betrayal of trust: These scams most commonly come from a member of the victim's own family within New Zealand.

The number of complaints filed by Kiwi scamming victims to cybersecurity watchdog group CERT NZ has spiked during the first three months of this year to 506 - the highest number on record.