"Two Croatian Air Force MIG-21s which are part of NATO's integrated air defence system intercepted in southern Croatia between 11 am and noon on Monday a civilian plane which had entered Croatia's air space," state agency Hina said on Monday, carrying a Defence Ministry press release.

The passenger plane was a US-registered Beechcraft 35-B33 which took off in Greece to Slovenia, the ministry said, adding that flight control was unable to establish radio contact with it.

Following a command from NATO’s Combined Air Operations Centre in Torrejon, Spain, the two Croatian MIG-21s took off to intercept and identity the plane.

After the Croatian pilots saw that it was a civilian plane, the MIG-21s returned to base in Zagreb.

When contact was made with the plane, it was established that avionics had failed, and the plane continued towards Slovenia as planned.

The interception was conducted in line with NATO rules and procedures, the ministry said, adding that its success confirmed the capability of Croatia’s airspace control and protection system as well as the advantages of participating in NATO’s integrated air defence system.

Hina did not say where the interception happened.