WASHINGTON (Reuters) - Financial crime fighters at the U.S. Treasury are “aggressively” pursuing virtual currency platforms that lack strong internal safeguards against money laundering, a top official told a Senate panel on Wednesday.

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With more criminals using the emerging asset class to store and transmit their ill-gotten gains, Treasury’s Financial Crimes Enforcement Network (FinCEN) will pursue malfeasant virtual currency platforms even if they are located overseas, Sigal Mandelker, the U.S. Treasury Department’s under secretary for terrorism and financial crimes, told the Senate Banking Committee.

U.S.-based platforms for bitcoin and other virtual currencies are required to comply with antimoney laundering (AML) rules including filing suspicious activity reports, with around 100 such platforms registered with FinCEN. But many other countries have no such requirements.

“The real vulnerability that we all have to address is that while we have regulatory authorities in place here in the United States and we do enforce those ... we need other countries to do the same,” Mandelker told the committee’s hearing on U.S. antimoney laundering laws.

Mandelker said the U.S. government would also encourage other countries to introduce stricter regulation of virtual currencies, which law enforcement officials say are attractive to criminals making illegal transactions because they can be used anonymously.

In July, the Treasury moved to shut down the website of Russia’s BTC-e exchange, one of the world’s largest bitcoin platforms, and ordered it to pay a $110 million fine for allegedly facilitating transactions involving ransomware, computer hacking, and drug trafficking, among other crimes.

A U.S. jury also indicted a Russian man in July in connection with the alleged crimes perpetrated by the platform.

Regulators and governments around the world are still debating how to address risks posed by cryptocurrencies. In recent weeks, South Korea, Japan and China have all made noises about a regulatory crackdown while officials in France vowed to investigate the emerging asset class.

Senators on Wednesday expressed concerns over the risks posed by cryptocurrencies to the global financial system with Democratic Senator Mark Warner saying the U.S. had “a lot of work to do” to get a grip on the issue.

U.S. markets regulators said this month they plan to take more aggressive enforcement action against exchanges that may be defrauding investors or allowing market manipulation.

The price of bitcoin slumped to $10,000 on Wednesday, halving in value from its peak price of almost $20,000 hit just in December, with investors gripped by fears regulators could clamp down on the volatile currency.