WASHINGTON — The Internal Revenue Service issued $4 billion in fraudulent tax refunds last year to people using stolen identities, with some of the money going to addresses in Bulgaria, Lithuania and Ireland, according to an inspector general’s report released Thursday.

The IRS sent a total of 655 tax refunds to a single address in Lithuania, and 343 refunds went to a lone address in Shanghai.

In the U.S., more fraudulent returns went to Miami than any other city. Other top destinations were Chicago, Detroit, Atlanta and Houston.

The IRS has stepped up efforts to fight identity theft, but thieves are getting more aggressive, said the report by J. Russell George, Treasury’s inspector general for tax administration.

Last year, the IRS stopped more than $12 billion in fraudulent refunds from going to identity thieves, compared with $8 billion the year before.

Thieves often steal Social Security numbers from people who don’t have to file tax returns, including the young, the old and people who have died, the report said. In other cases, thieves use stolen Social Security numbers to file fraudulent tax returns before the legitimate taxpayer files.