The US justice department said on Monday that it halted a series of healthcare fraud schemes that sought to bilk the federal government out of $14.6bn.

The operation, which the department called the largest healthcare fraud initiative in its history, led to criminal charges against 324 defendants and the seizure of more than $245m in cash, luxury cars and other assets. The actual loss to the US government totaled about $2.9bn, officials said.

“Today marks a decisive moment in our fight to protect American taxpayers from fraudsters and to defend the integrity of America’s healthcare system,” Matthew Galeotti, the head of the justice department’s criminal division, told reporters during a press conference.

Those charged include 93 doctors and other medical professionals accused of submitting false claims to government healthcare programs like Medicare and Medicaid.

Some of the schemes were run by transnational criminal organizations based outside the US, that have been perpetrating increasingly complex fraud operations targeting the American healthcare system, justice department officials said.

One such scheme, which prosecutors said was run out of Russia and eastern European countries, led to charges against 19 defendants, 12 of whom have been arrested.

The group used a network of foreign straw owners to buy dozens of US medical supply companies and, using stolen American identities, submitted more than $10bn in fraudulent claims to Medicare, according to the justice department.

Among those whose identities were compromised was Gerald Quindry, a 73-year-old retired engineer on Medicare. He was billed $15,500 for urinary catheters, though his doctor never ordered them nor did Quindry want nor receive them, as the Washington Post reported.

Quindry – who told the Post, “obviously, somebody deserves to be in jail” over the plot – had complained to Medicare, but program representatives had initially seemed unbothered.

“It’s not being done by small-time operators,” said Dr Mehmet Oz, the administrator for the Centers for Medicare & Medicaid Services. “These are organized syndicates who are designing to hurt America.”

• Guardian staff contributed