Found 1953 story in Dutch online newspaper archives. In night of 18/19 May 1953 Lt. Roman Petrowitsj Bondarenko parachuted from his plane some 20 kms. north of Zagreb when fire had broken out at 6.000 m altitude. Pilot was found a few days later.
The Russians had been looking for pilot and plane when they had gone missing on his/its training flight. Plane had taken off near Wien.
Crash also mentioned in British, French, American and more newspapers.
Perhaps also try the Austrian online newspapers (see
https://anno.onb.ac.at/anno-suche#se...=period&from=1), with note that full text may not be visible yet (70-yr. limit).
Regards,
Leendert