Police in Istanbul, Turkey, have been ordered to down helicopters, according to news alerts on social media, The Sydney Morning Herald reports.

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

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.

Eight members of Turkey's military who reportedly supported the coup landed in Greece after the failed attempt at regime change. They were arrested by Greek authorities but requested asylum.

Turkey has widened a crackdown on suspected supporters of a failed military coup as the government claims it's back in control of the country and the economy.

Authorities have rounded up 6000 people.

The foreign ministry has raised the death toll to more than 290, including over 100 rebels, and says 1,400 people were hurt.