Chinese President Hu Jintao visited Croatia on 19-20 June.
Dragun told Hina today that the protest note was about two Croatian MIG planes engaged in the protection of the Chinese head of state during his arrival in Zagreb.
In this regard Croatia notified Slovenia that there would be flights above the border area, the spokesman said.
The Slovenian news agency STA said today that two Croatian combat aircraft, which were escorting a foreign delegation, violated Slovenia's airspace on June 19, prompting Slovenia to send a protest note to the Croatian ambassador in Ljubljana, Svjetlan Berkovic.
The Croatian foreign and defence ministries will work on establishing facts and inform Slovenia about that, Dragun said.
He added that Croatian combat planes were also engaged in the protection of other heads of states, including U.S. President George W. Bush and Russian President Vladimir Putin, during their arrivals in Zagreb.
According to sources close to the Croatian Defence Ministry, Slovenian small sports aircraft violate the Croatian airspace at least three or four times a month.