WASHINGTON (AP) — A Treasury report says the Internal Revenue Service issued $4 billion in fraudulent tax refunds last year to people using stolen identities.

Many refunds were sent overseas, including 655 sent to a single address in Lithuania.

The report by the agency's inspector general says the IRS has stepped up efforts to fight identity theft, but thieves are getting more aggressive.

Last year, the IRS stopped more than $12 billion in fraudulent refunds from going to identity thieves. That's up from $8 billion the year before.

The report says thieves often steal Social Security numbers from people who don't have to file tax returns, including people who are young, old or deceased.

In other cases, thieves use stolen Social Security numbers to file fraudulent tax returns before the legitimate taxpayer files.