New York's financial regulator has asked Lloyd's Banking Group Plc and Swiss RE AG for details about dealings linked to Iran as part of a probe into 20 non-U.S. reinsurance firms, the Wall Street Journal reported.

Citing a copy of the letter, the newspaper said Benjamin Lawsky, superintendent of New York's Department of Financial Services, had written to the reinsurance firms asking for details about their business with people or entities linked to Iran after finding evidence that at least three firms insured shipments to Iran.

Lloyd's and Swiss RE were not immediately available comment outside regular business hours.

The United States and the European Union imposed sanctions on Iran last year that include restrictions on insuring shipments. The measures are aimed at making it hard for Iran to sell oil, and limit funds to its nuclear program which countries in the West believe is being used to develop weapons.

Iran says the program is purely for civilian purposes.