Turkey has called a meeting of Nato member states to discuss its response to the shooting down of one of its warplanes by Syrian forces on Friday.Ankara has invoked Article 4 of Nato’s charter, under which consultations can be requested when an ally feels their security is threatened, officials say.Earlier, Turkey’s foreign minister said the F-4 Phantom was in international airspace when it was shot down.Syria has insisted the jet was engaged while it was inside its airspace.It has also said no act of hostility was intended, noting that as soon as the military discovered the "unidentified” aircraft was Turkish its navy joined efforts to rescue the two crew members.The Turkish foreign ministry said it knew the coordinates of the jet, which was in Syrian territorial waters at a depth of 1,300m (4,265ft), but has not yet found it.The coast guard is still searching for the crew in the Mediterranean Sea, though hopes are fading of them being found alive. he government has also issued a diplomatic protest note to Syria.‘Training mission’Nato spokeswoman Oana Lungescu said the North Atlantic Council, the principal political decision-making body within the military alliance, would meet in Brussels on Tuesday to discuss the incident."Turkey has requested consultations under Article 4 of Nato’s founding Washington Treaty,” she told Reuters."Under article 4, any ally can request consultations whenever, in the opinion of any of them, their territorial integrity, political independence or security is threatened.”Turkey wants to be sure of the strongest backing once it decides its official response, reports the BBC’s Jonathan Head in Istanbul.The government has promised that it will be strong, decisive and legitimate, and that it will share all the information it has with the public.Earlier, Foreign Minister Ahmet Davutoglu became the first senior Turkish official to challenge Syria’s account of the downing of the jet.After lengthy meetings with military chiefs, he told TRT state television that the unarmed jet had "momentarily” entered Syrian airspace by mistake on Friday but had left when it was shot down 15 minutes later."According to our conclusions, our plane was shot down in international airspace, 13 nautical miles (24km) from Syria,” he said. According to international law, a country’s airspace extends 12 nautical miles (22.2km) from its coastline, corresponding with its territorial waters.