The U.S. government announced Monday a crackdown on online operators that market illegally replicated products, resulting to the seizure and immediate closure of 150 Web sites, most operating from China.

A joint operation by the Immigration and Customs Enforcement and the Federal Bureau of Investigation led to the closure of 150 sites that according to U.S. Assistant Attorney General Lanny A. Breuer were involved in peddling fake items from Louis Vuitton to NBA jerseys.

Millions have been amassed by these illegal online entrepreneurs, according to ICE Director John Morton while thousands of unsuspecting Americans have been made to believe they were buying the real thing.

"This is straight crime ... people being duped into buying a counterfeit," Morton told the Associated Press.

With the latest breakthrough, FBI and ICE officials said that as many as 350 Web sites have been closed down by U.S. authorities since the campaign against illegal online businesses was launched in June 2010.

As in previous cases, the newly seized sites now greet prospective customers with a uniform message, informing them that the domain has been confiscated by the U.S. government, the AP report said.

The new 'greeting' also warned visitors of the shut-down sites that "willful copyright infringement is a federal crime."

While most of the sites targeted by the ICE, Morton said, were registered by their owners in the United States, no one has been charged by authorities nor funds purportedly earned by the bogus sites have been recovered.

That is because almost every site owners were based in Asia, specifically in China, though both Breuer and Morton gave assurances that they will continue their investigations to collect more information on these operators.

Illegal operations of questionable Web sites have been linked by the FBI to possibly more serious activities such as the sale of pirated DVDs in many Asian countries, proceeds of which, intelligence sources said, were funneled to the operations of Islamist insurgents in the region.

"We are worried about organized crime and (that profits) are going to fuel other criminal activity," Morton confirmed.