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Serbian President Tomislav Nikolic had to postpone an official visit to the Vatican on Friday when his plane developed engine trouble and had to return to Belgrade.
The visit, during which Nikolic was to meet Pope Francis, was "cancelled due to a failure of an engine of the plane", a spokesman for the presidency said.
The presidential Falcon 50 jet landed safely at Belgrade's Surcin airport.
One of the plane's three engines stopped working while it was at an altitude of 10,000 metres (32,800 feet) above the Adriatic sea, the state-run RTS television reported.
An accident was avoided due to an experienced pilot, it said.
Nikolic's visit to the Holy See had been aimed at confirming the "good relations between the Vatican and Serbia" whose 7.1 million inhabitants are mostly Orthodox Christian, Serbian authorities said earlier.
Meanwhile, an advisor to Nikolic said that his visit to the Vatican had been postponed "until a new date is determined."
"We hope that the visit will take place soon," advisor Stanislava Pak told the state-run Tanjug news agency.
The Serbian head of state attended the inauguration ceremony of Pope Francis in March 2013.
Friday's incident was not the first on the jet, produced in 1981, which is also used by the Serbian government. It also experienced technical problems in 2010, 2011 and 2012.