President Erdogan, used FaceTime, to communicate to news broadcasters.
In calling for protest, he said he would be returning to the capital Ankara.
He said he believed there was a minority of the army involved and those responsible would face the "necessary response".
The army seized media outlets, including the state-run TRT channel.
One of the channel's presenters read a statement from the military.
She said Turkey's democratic and secular rule of law had been eroded by the current government.
The country is now run by a "peace council" that will ensure the safety of the population, the announcer added.
A new constitution will be prepared "as soon as possible", the statement said.
Shortly after the statement was read the broadcaster was taken off the air.
Access to Facebook, Twitter and YouTube was also reportedly blocked in Turkey.
However, Twitter said it believed its service was slowed rather that totally blocked.
It followed after a statement from the military group read out on NTV television said: "The power in the country has been seized in its entirety."
The Dogan agency reported that the statement said that the military did this "to reinstall the constitutional order, democracy, human rights and freedoms, to ensure that the rule of law once again reigns in the country, for the law and order to be reinstated".
The military statement went on to say that "all international agreements and commitments will remain. We pledge that good relations with all world countries will continue".
It is not clear who is behind the action.
Broadcaster CNN Turk reported President Recep Tayyip Erdogan was "safe" but did not elaborate.
Offices of President Erdogan's AKP party have reportedly been taken over.
Earlier the country's prime minister addressed the nation.
He said Turkey's military engaged in an attempted coup.
Binali Yildirim told NTV television: "It is correct that there was an attempt."
Mr Yildirim did not provide details, but said Turkey would never allow any "initiative that would interrupt democracy".
Earlier, military jets were heard flying over the capital, Ankara.
Media reports said ambulances were seen in front of Turkey's military headquarters.
"We are focusing on the possibility of an attempted (coup)," Mr Yildirim said.
"There was an illegal act by a group within the military that was acting out of the chain of military command. Our people should know that we will not allow any activity that would harm democracy."
The Dogan news agency says one-way traffic on the Bosphorus and Fatih Sultan Mehmet bridges - the main links between the European and Asian sides of Istanbul were blocked. Video footage showed the bridge being blocked by military vehicles.
"Those behind the attempted coup would pay the highest price," added the prime minister.
In the capital Ankara, warplanes and helicopters roared overhead. A Reuters journalist heard gunshots.
Dogan News Agency reported the national police directorate had summoned all police to duty in Ankara.
All flights from Istanbul's Ataturk airport have been cancelled after tonight's events, according to a Reuters witness citing a pilot at the airport.
Washington-Saudi Foreign Minister says he can't speculate about the events taking place.
While coups have been common in the country's history, this is the first military intervention in almost 20 years.