A Turkish government official has told the Telegraph (and other media organisations) that the action was not against a specific country and that they warned the aircraft. The official said the plane ignored their warnings and flew over Turkey,

In line with the military rules of engagement, the Turkish authorities repeatedly warned an unidentified aircraft that they were 15km or less away from the border. The aircraft didn't heed the warnings and proceeded to fly over Turkey. The Turkish Air Forces responded by downing the aircraft.

"In the past, we have made public our military rules of engagement and reminded our counterparts that any violation of Turkish airspace would trigger the actions prescribed by the MRoE. This isn't an action against any specific country: Our F-16s took necessary steps to defend Turkey's sovereign territory.

The Times' Defence Editor tweets that Nato will hold an extraordinary session today in light of the morning's events.

This map shows the alleged route of the plane (in red), according to the Turkish government.