Image caption Some films were available online hours after their cinema release

US officials have shut down nine websites accused of offering free access to films, including Toy Story 3.

The crackdown, which included seizing assets from 15 bank accounts, involved police, customs and the movie industry.

The closure of the sites, which had 6.7m visitors combined each month, was described as the "largest takedown of illegal movie and TV websites in a single action" by the government.

Some films were available hours after their release in US cinemas.

Previous crackdowns on film piracy have focused on illegally copied DVDs.

The latest action is the first of its scale to target websites which profit - by selling advertising or taking donations - from offering pirated films for free.

Website warning

Search warrants were executed in New Jersey, New York, North Carolina and Washington in an investigation which involved about 100 agents in 11 US states as well as the Netherlands

Websites targeted had links to films including Knight and Day, Jonah Hex and Prince of Persia: The Sands of Time - all currently showing in US cinemas.

If a site reappears, so will we. If the criminals move overseas, we will follow John Morton, Immigration and Customs Enforcement

A warning placed on the websites state they have been seized by officials.

The government has only seized domain names which means computers running the sites could be used with different URLs.

John Morton, of Immigration and Customs Enforcement, said: "If a site reappears, so will we.

"If the criminals move overseas, we will follow.

"Take it from me, I don't think that we've stopped internet piracy in a day but this is going to be a sustained effort."

Officials say that further actions, including possible prison terms, are expected against website operators.