U.S. Immigration and Customs Enforcement's (ICE) Homeland Security Investigations division, along with the U.S. Department of Justice, seized the websites in the past week, ICE said in a press release. The U.S. operation, nicknamed Bitter Pill, was part of an Interpol operation aimed at disrupting organized crime networks allegedly behind illegal online drug sales.

The new seizures by ICE and the DOJ nearly double the number of websites shut down by the agencies in the name of copyright enforcement. As of July, the for alleged copyright infringement over the past two years.

Civil liberties groups have criticized the seizure efforts, saying they lack due process for the website owners. In August, the against two sports streaming websites after shutting them down for 17 months.

The new worldwide effort, involving 100 countries, resulted in 79 arrests and the seizure of 3.7 million doses of counterfeit medicines worth an estimated US$10.5 million, ICE said. Worldwide, about 18,000 websites were shuttered during the weeklong operation, which ended Tuesday.

"These international partnerships are essential in the global fight against the trafficking of counterfeit drugs," ICE Director John Morton said in a statement. "Instead of taking potentially life-saving medicines, customers are duped into purchasing drugs that are fake or untested and could ultimately do them more harm than good."