The top Greek official for European and Cypriot affairs, his son and four other people were killed tonight when their small jet passenger plane ran into heavy turbulence over Romania and plummeted 19,000 feet before leveling off, officials here said.

The Greek Information Ministry said Deputy Foreign Minister Yiannos Kranidiotis and his 23-year-old son Nikos were pronounced dead of as yet undetermined injuries after the pilot, who was not injured, landed the twin-engine aircraft here. Also killed were the plane's engineer, Kranidiotis's bodyguard and two journalists; two other passengers were seriously injured.

The cause of death for any of the victims was not clear, but all six were apparently thrown about the cabin when the Falcon executive jet plunged from an altitude of 23,000 feet to 4,000 feet within seconds. A Greek journalist who was on board told Greek television that those killed were apparently not strapped in their seats and that Kranidiotis was standing and briefing reporters when the plane suddenly lost altitude.

Kranidiotis, 51, was on his way from Athens to Bucharest for a meeting of Balkan foreign ministers when the incident occurred, Greek and Romanian officials said.

"We are very shaken, the whole government, the whole ministry" said Greek Foreign Minister George Papandreou. "I personally can't believe it. We lost people giving a battle for peace in the Balkans. I've lost a friend. . . . Greece and Cyprus have lost a tireless worker for human rights."

Kranidiotis, a Cypriot-born lawyer, was general secretary of the foreign ministry for European affairs from 1994 to 1995 before becoming a deputy foreign minister. Earlier this year, he was promoted to the number two position in the ministry and concentrated on European and Cypriot affairs. He studied at Harvard University and Britain's Sussex University and authored several books on Greece and Cypriot politics. Nikos was his only child.