The U.S. government sued Swiss banking giant UBS AG on Thursday, asking a federal court to order UBS to disclose to the Internal Revenue Service the identities of the bank's U.S. customers with secret Swiss accounts, the Justice Department said.

According to the lawsuit, as many as 52,000 U.S. customers hid their UBS accounts from the government in violation of tax laws, the department said.

The lawsuit filed in Miami came the day after UBS agreed to pay $780 million and identify certain U.S. clients in a deal to resolve criminal fraud charges that it assisted rich Americans to evade taxes.

(Reporting by James Vicini, Editing by Tim Dobbyn)