Sofia  - The chief executive of the European Union's anti- fraud watchdog OLAF warned Bulgaria Thursday that it must begin convicting corrupt officials, or risk losing the battle against organized crime.

OLAF director Franz-Hermann Bruener met Prime Minister Sergey Stanishev, Deputy Premier in Charge of EU Funds Management Meglena Kuneva and other officials and press to review the results in probes into embezzlement of development aid sent by Brussels.

This year the EU froze nearly 500 million euros (630 million dollars) in development programmes to Bulgaria, a member-state since 2007, amid suspicion of massive embezzlement schemes.

Though OLAF tipped Bulgarian authorities about widespread embezzlement of funds more than two years ago, the first trial of corrupt officials was launched in late October.

Bulgarian courts however were also criticized by the EU for inefficiency and suspected corruption, so convictions are not guaranteed even if cases make it to court.

"Without real convictions, Bulgaria's combat with corruption may come into doubt," Bruener was quoted as saying after meeting Bulgarian officials. (dpa)