Turkish Prime Minister Binali Yildirim has announced that a group of military forces have engaged in a "coup attempt" against the government.
Yildirim made the announcement late on Friday, as he vowed that the "perpetrators" will be contained.
He said that a number of generals are involved in the takeover of the government, adding that it "will never give up democracy".
Al Jazeera has learned that Istanbul's Ataturk international airport has been shut down, and all flights have been cancelled.
An Al Jazeera reporter in Istanbul also reported seeing shops closing their doors in the Taksim Square area.
"People are going home now," he said.
Istanbul's Bosphorus Bridge and Fatih Sultan Mehmet Bridge have also been shut down by the Turkish army, local television channels reported, without giving a reason.
The two major bridges connect the Asian side of Istanbul to the European side.
Dogan News Agency footage showed cars and buses being diverted, according to Reuters.
Reuters witnesses in Istanbul, Turkey's largest city, also spotted helicopters overhead.
"It seems there is dissent in the military ranks," Al Jazeera's Zeina Khodr, reporting from Gaziantep, said.
In the capital Ankara, gunshots were heard, as military jets and helicopters were seen flying overhead, a Reuters witness said.
Turkey has had a history of coup attempts, the last time being carried out in 1997, which forced the resignation of then-prime minister Nemettin Erbakan.