State-run Anadolu Agency reported early Saturday that a bomb has hit the Turkish parliament in Ankara in the midst of an attempted coup.

CNN-Turk television reported some police officers and parliament workers were hurt in the bomb attack.

Elsewhere, Anadolu reported 17 police officers have been killed in a helicopter attack on police special forces headquarters near Ankara.

The agency said Turkish Air Force planes were flying above Turkey's capital early Saturday to strike at helicopters used by those attempting a coup.

Turkish broadcaster NTV reports that a Sikorsky helicopter in possession of the army group has been downed by a Turkish military F-16 jet.

In Washington, President Obama urged all parties in Turkey to support the government of President Recep Tayyip Erdogan.

Earlier, Turkish news agency Dogan reported soldiers fired on people trying to cross Istanbul's Bosporus bridge and some are wounded.

Deputy Prime Minister Numan Kurtulmus said on live television that Turkey's ruling Justice and Development Party is still in charge of the government, according to the BBC.

Military units patrolled the streets and seized key bridges as the Turkish military declared martial law and said in a statement read out on Turkish television that it had "fully seized control" of the country.

In response, Erdogan, speaking from an undisclosed location, surfaced via FaceTime on CNN Turk calling on the Turkish people to take to the public squares and go to the airport.  "I've never seen anything more powerful than the people," he said.

The president’s office would not reveal Erdogan’s whereabouts, saying only that he is at a secure location.

A senior US military source tells NBC News that Erdogan, refused landing rights in Istanbul, is reported to be seeking asylum in Germany. The report could not immediately be independently confirmed.

As both sides claimed the upper hand, Turkish Prime Minister Binali Yildirimchallenged the military's claim that it was in charge, saying only that there had been "an uprising," according to the Hurriet Daily News.  He said Turkey would never allow any “initiative that would interrupt democracy.”

Meanwhile, Turks poured out into the streets despite the sound of explosions and gunfire in Istanbul.

In Ankara, the U.S. Embassy issued an emergency message reporting that many bridges had been shut down in Istanbul and that shots have been heard in Ankara. It said the government claimed that its security forces were taking action to contain it.

"We encourage U.S. citizens to shelter in place and do not go the U.S. Embassy or Consulates at this time," the embassy said. "Monitor local press for updates, avoid areas of conflict, and exercise caution if you are in the vicinity of any military or security forces." The U.S. Air Force operates out of the Incirlik Air Base in south central Turkey.

There have been three successful coups in Turkey, a NATO ally, since 1960, and in 1997 the military carried out a "soft" coup, issuing directives to the Turkish government that it was forced to accept. The military has cast itself as the traditional protector of secular, democratic rule.

As the coup attempt unfolded, security forces in Istanbul blocked two bridges connecting the Anatolian side to the European side of the city. Travelers reported on their Twitter accounts that airliners were stopped from taking off, while military aircraft were seen flying over Ankara, the capital.

Dogan News Agency reported that police in Ankara called personnel to their officers. In addition, media reports said ambulances were seen in front of the Turkey’s military headquarters.

State-run Anadolu Agency is reporting that Chief of General Staff Hulusi Akar is being kept as a hostage, according to Hurriet Daily News.

CNNTürk reported that the coup attempt got underway in Ankara when two busloads of soldiers entered the headquarters of the state-run TRT news agency, and that the channel then started to broadcast a stream of weather forecasts, Hurriet reported.