BUCHAREST, Romania (AP) _ Greece's deputy foreign minister and five others were killed late Tuesday when their executive jet hit heavy turbulence and plummeted thousands of feet before leveling off, Romanian officials said.

Deputy Foreign Minister Yiannos Kranidiotis, his son and four others were killed, said Romanian Transport Minister Traian Basescu. He said five others injured had been hospitalized.

The pilot was unhurt and was able to land the government-owned Falcon executive jet in Bucharest, Basescu said.

The cause of the deaths wasn't immediately clear. Romanian television reports said Kranidiotis and the others possibly suffocated or suffered heart attacks after their aircraft suddenly depressurized as it rapidly lost altitude.

Basescu said the aircraft hit heavy turbulence and quickly dropped from 23,000 feet to 4,000 feet before the pilot regained control.

The incident occurred shortly after the plane entered Romanian airspace near Giurgiu, 40 miles southeast of Bucharest.

Among the others killed were Kranidiotis' son, the plane's mechanic and two journalists accompanying the deputy minister, Greek media reported. A description of the last victim wasn't immediately available.

The Greek delegation was on its way to Bucharest for a meeting of Balkan countries.

No further information was immediately available.