Franco Frattini had a brief meeting with President Georgi Parvanov, and was also due to hold talks with Prime Minister Sergei Stanishev.
Bulgaria is hoping to join the EU on Jan. 1 along with neighboring Romania, but has been told it must make clear progress in fighting corruption and crime or face the prospect of a year's delay. A final decision is expected in September.
Despite a string of mafia-style slayings in recent years and frequent reports of alleged high-level corruption, there have been no prominent arrests, according to the AP.
An attempt to gain control of the Turkish UAV Bayraktar TB2 ended with the destruction of the Russian Avtobaza-M complex