Bulgaria hunts for mystery pilot who flew across several European countries

Bulgarian authorities are searching for a mysterious pilot who flew unauthorised across several European countries.

Defence forces in the country were placed on high alert on Wednesday evening when a small aircraft was detected in its airspace.

The two-seater Beechcraft plane had apparently departed from Hungary and flown over Poland and Slovakia, according to Interior Minister Boiko Rashkov.

The pilot is then believed to have landed near the Black Sea, after briefly crossing into Serbia and Romania.

The 60-year-old aircraft was finally found with its engine still warm on the runway of a private airport in the northeast area of Buhovtsi. It was covered by a tarpaulin and there was no trace of the crew.

The suspicious aircraft had no flight plan, had deactivated its transponders and did not respond to radio messages or visual signals, Bulgaria's defence ministry said in a statement.

The Beechcraft plane was also tracked and escorted by Hungarian and Romanian fighter jets.

Bulgarian defence minister Dragomir Zakov told reporters that the aircraft "did not represent a threat at any time".

"It was flying at a very low altitude and with low speed, which makes interception by fighters difficult," he added.

The prosecutor's office in Varna, eastern Bulgaria has opened an investigation into the incident.