Police in Istanbul, Turkey, have been ordered to down helicopters, according to news alerts on social media.

Separately, CNN Turk reports that 42 helicopters remain missing from the military after the failed coup over the weekend.

Greek policemen check a Turkish Blackhawk helicopter after landing at the airport of Alexandroupolis, northeastern Greece, on Saturday. Credit:AP

The coup attempt, which involved significant sections of Turkey's military, made ample use of military helicopters in a failed effort to end President Recep Tayyip Erdogan's rule.