The US authorities have blocked access to three websites offering pirated copies of Android apps. The Department of Justice said it was the "first time website domains involving cell phone app marketplaces have been seized". The sites involved were applanet.net, appbucket.net and snappzmarket.com. Their pages now display a FBI warning that first-time offenders involved in copyright infringement face up to five years in jail. "The theft of intellectual property, particularly within the cyber-arena, is a growing problem and one that cannot be ignored by the US government's law enforcement community," said the FBI in a statement. "These thefts cost companies millions of dollars and can even inhibit the development and implementation of new ideas and applications." International effort The agency said search warrants had been executed in six areas of the country including Georgia, Florida, Mississippi and Texas. In addition it said international law enforcers, including officials from France and the Netherlands, had helped seize evidence from computer servers based outside the US, which had hosted most of the websites' content. Sally Quillian Yates, US attorney for the Northern District of Georgia, signalled other sites faced similar action. "We will continue to seize and shut down websites that market pirated apps, and to pursue those responsible for criminal charges if appropriate," she said. Although this is the US's first seizure of app-piracy net domains, it follows other efforts against file-sharing sites. Agents shut down Megaupload earlier in the year, following complaints by the Motion Picture Association of America and others. The US is currently seeking to extradite its co-founder Kim Dotcom and other employees from New Zealand. The Ukrainian press has also suggested its government pressured a local internet service provider into taking BitTorrent link-tracking site Demonoid offline in order to impress the US. The action coincided with a visit by Ukrainian First Deputy Prime Minister Valeriy Khoroshkovsky to Washington. Widespread piracy Complaints about app piracy have repeatedly made the tech headlines over recent months. In April games maker Sports Interactive complained that for every 10 copies of its football-management simulation, nine had been illegally downloaded. Three months later Czech Republic-based Madfinger Games announced it would give away copies of a zombie-themed game after seeing "giant" piracy rates, despite the fact it had only charged $1 (63p) for the app. Edinburgh-based software engineer Matt Gemmell subsequently suggested that the "open" nature of Android - in which apps can be installed from outside Google's Play marketplace - had contributed to the problem. But another developer, Jack Palevich, reported that his firm had experienced a higher piracy rate on Apple's iOS platform due to users "jailbreaking" their phones. The technique allows them to bypass the iPhone maker's efforts to restrict them to programs offered in its store. The Software and Information Industry Association told the BBC that it had been flagging the issue to the US government for years. But despite the FBI's warning that first-time copyright infringers could face jail time and up to $250,000 (£158,265) in fines, the lobby group's lawyer, Keith Kupferschmid, said he thought any punitive action would be limited to offending sites' administrators. "I would be very surprised if either the US government or other government or the copyright holders went after the downloaders themselves," he said. "History has shown they will go after the big fish - the people making the material available to be downloaded. "And if the individuals involved are outside the US, I would expect other countries to become involved in the process."