The Erdogan regime has carried out a purge of civil servants suspected of ties to the movement, seized businesses and closed some media organizations. Access to social media has been obstructed during previous periods of political upheaval in the country, according to some Internet watchdog groups, although Turkish authorities have denied involvement and suggested that technical problems were to blame. Kerry says he spoke this evening to Turkish Foreign Minister Mevlut Cavusoglu and emphasized the United States' absolute support for Turkey's democratically-elected, civilian government and democratic institutions. CNN-Turk television reported some police officers and parliament workers were hurt in the bomb attack. The person, who spoke on condition of anonymity for security reasons, also said fighter jets were flying low in the area. In an expression of support for President Tayyip Erdogan and his government, Stoltenberg said: "I call for calm and restraint, and full respect for Turkey's democratic institutions and its constitution." 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. 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. 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. Turkey's state-run Anadolu Agency says that 17 police officers have been killed in a helicopter attack on police special forces headquarters on the outskirts of Ankara. The European Union's foreign policy chief called for "restraint and respect for democratic institutions" in Turkey after the military said that it seized control of the country. Turkish news agency Dogan has reported that soldiers have opened fired on people trying to cross Istanbul's Bosporus bridge in protest of the attempted coup, and some have been wounded. Turkey's Istanbul-based first army commander says the soldiers involved in an attempted coup "represent a small group" and "there is no cause for concern," according to the state-run Anadolu Agency. Turkish Interior Minister Efkan Ala says very effective units from the chief of general staff's office, the Turkish armed forces and the police are responding to the attempted coup in the country. Independent observers noted that the 1949 treaty that created the U.S. alliance has no mechanism for suspending members, unlike the United Nations, the European Union or the Organization of American States. Nothing in NATO's founding 1949 Washington Treaty says anything about intervening in the internal or political affairs of an alliance member, and Turkey kept its NATO membership following past military coups. The treaty's key clause, Article 5, stipulates that NATO member states agree that "an armed attack against one or more of them in Europe or North America shall be considered an attack against them all," but that language has taken to apply to an external enemy. Turkey's state-run news agency report military helicopters have also attacked the headquarters of TURKSAT satellite station on the outskirts of Ankara and the Ankara Police headquarters. Dozens of tanks were seen moving toward a palace that is now used by the prime minister and deputy prime ministers. 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. 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."