Around 1,800 special forces are joining the police in securing Istanbul on Monday, as part of strong measures enacted in the aftermath of a failed military coup, Turkish media said.

Extraordinary security measures have been observed in the metropolis, as special forces and police accompanied by armored vehicles patrol scores of avenues and streets.

Special teams have also taken their positions at key installations across the city, press 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 coup attempt that broke out on Friday night.

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

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 had ordered his teams to shoot down all the unidentified helicopters flying over the city, the Hurriyet daily said.

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

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