HANOI (REUTERS) - Vietnamese police have arrested four men accused of defrauding more than 5,000 Americans trying to buy Covid-19 protective equipment online out of nearly US$1 million (S$1.3 million), the Ministry of Public Security said on Thursday (Aug 20).

The arrests of the four, aged between 22 and 36, were made following a joint investigation by the ministry and US Department of Homeland Security's Office of Homeland Security Investigations, the ministry said in a statement on its website.

In March, the four began operating 110 websites that offered personal protection equipment (PPE), including hand sanitisers, masks and disinfectant wipes, and received money from the Americans via their Paypal accounts, the ministry said.

The four never had the products offered on the websites and their victims never received what they paid for, the ministry said.

"This investigation resulted in significant financial losses to people who were already facing enormous challenges due to the Covid-19 pandemic," US Ambassador to Vietnam Daniel Kritenbrink said in a statement on the embassy's website.

Speaking at a regular press briefing on Thursday, foreign ministry spokeswoman Le Thi Thu Hang said Vietnam was determined to "prevent and strictly deal with any trade fraud" and highly appreciated the coordination from the United States.

The ministry said the four had been charged with"appropriation of property using a computer network, telecommunications network or electronic device", a crime that carries a prison term of up to 20 years.

Reuters could not immediately reach their lawyers for comment.