Istanbul: Around 1,800 Special Forces troops joined Turkey police in securing Istanbul on Monday, as part of strong measures enacted in the aftermath of a failed military coup, the media reported.

Extraordinary security measures have been observed in the metropolis, as Special Forces and police personnel accompanied by armoured vehicles patrolled avenues and streets.

Special teams have also taken their positions at key installations across the city, reports said.

On Monday morning, the Turkish Air Force Academy located near Ataturk Airport was raided by a large number of security forces, with four high-ranking soldiers reportedly taken away over their links to the failed coup attempt on Friday night.

President Recep Tayyip Erdogan, who has been in Istanbul since early Saturday, ordered overnight patrols across the country by F16 fighters.

According to the broadcaster, Erdogan made the order over unusual aerial activities observed over northwestern cities of Canakkale and Balikesir.

In the meantime, Istanbul’s police chief Mustafa Caliskan ordered his teams to shoot down all unidentified helicopters flying over the city, a daily reported.

All the tarmacs for choppers in Istanbul have been put under police control, and flights over the city have been restricted.

A harsh crackdown was underway in Turkey following the coup, with the arrest of thousands of suspects from the military, the police and the judiciary.