The Latest on what appears to be an attempted military coup in Turkey (all times local):
The military has taken position at the base of the Taksim monument at Taksim square in Istanbul, occasionally firing into the air to disperse a growing crowd of government supporters.
Military helicopters are flying overhead and many police are in position, separate from the military.
Meanwhile, a nearby mosque just made an anti-coup announcement.
The leaders of Greece's armed forces and police are holding emergency meetings in Athens to monitor developments in neighboring Turkey, according to government officials.
The officials, speaking on condition of anonymity early Saturday because they weren't authorized to speak to the media, described the country's armed forces as being placed in a state of "heightened readiness" and not alert.
Despite markedly improved trade and relations between Greece and Turkey in recent years, the two countries have ongoing airspace and sea boundary disputes in the Aegean Sea. They also collaborate in implementing an agreement with the European Union -- monitored by NATO -- to limit the number of refugees and migrants traveling to Europe.
State-run ERT television reported that Greek Prime Minister Alexis Tsipras had been briefed by intelligence and military leaders on the coup attempt in Turkey, including unusual movements by Turkish armed forces before the attempt became apparent.
The White House says President Barack Obama has been briefed on developments in key NATO ally Turkey where the military claims to have seized power in a coup.
The National Security Council said Obama had been apprised of Friday "unfolding situation" in Turkey and would continue to get regular updates.
U.S. Secretary of State John Kerry says he hopes for stability and continuity in Turkey following the reports.
Kerry, in Moscow for talks with Russian officials on Syria on Friday, told reporters he didn't have details of the situation rapidly unfolding on the ground in Turkey and said it would be "inappropriate" to comment on developments. But, he expressed hope that the key ally and strategically important member of the coalition fighting the Islamic State would remain at peace.
Russian Foreign Minister Sergey Lavrov and other Russian officials have called on their countrymen in Turkey to stay indoors amid uncertainty about whether a military coup is taking place.
Lavrov made the statement early Saturday at a news conference with U.S. Secretary of State John Kerry. However, Lavrov, who had been in lengthy talks with Kerry, said he had little information about what was taking place in Turkey.
Russia's tourism authority issued a similar warning. Turkey had long been a popular vacation destination for Russians, but the numbers dropped sharply last year when Russia banned package tours to Turkey amid tensions over Turkey shooting down a Russian warplane and it was unclear how many Russians currently are in the country.
A Turkish military statement read on state TRT television says the military has seized power, citing rising autocratic rule and increased terrorism.
But CNN-Turk has quoted Defense Minister Fikri Isik as describing it as a "pirate statement."
Earlier, another statement published by the private Dogan news agency says that the military has "fully seized control" of the country.
A Turkish news agency has published a statement from the military saying the armed forces have "fully seized control" of the country.
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."
Turkey's prime minister says a group within Turkey's military has engaged in what appeared to be an attempted coup.
Binali Yildirim told NTV television: "it is correct that there was an attempt."
Yildirim didn't 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 the Turkey's military headquarters.