Istanbul - Up against the greatest challenge of his political career in facing down an attempted coup, Turkish President Recep Tayyip Erdogan was prepared to use any means to speak to the people.The president, who almost every day of his working life speaks to huge audiences from a podium, was forced to address Turks from a simple mobile phone.Astonished Turks saw the president, looking rattled and drawn, peer out of the screen not in person but from a smartphone.Presenters on the NTV and CNN-Turk channels, who seemed as astonished by the situation as anyone, held smartphones up to the camera with a microphone beneath to broadcast interviews with Erdogan to the world.The president appeared stressed but also defiant, issuing a call to supporters to rally in the streets which was rapidly followed in Ankara, Istanbul and Izmir."I certainly believe that coup plotters will not succeed," Erdogan told CNN-Turk television, speaking on FaceTime via mobile phone in his first reaction to the move."I urge the Turkish people to convene at public squares and airports. I never believed in a power higher than the power of the people." Erdogan said he was still president and Turkey's commander in chief, promising that plotters would pay a "very heavy price". He had not been seen in public for the last days, with the president believed to be taking his annual summer vacation on the Aegean Sea in the resort of Marmaris.He later gave a brief statement on the doorstep of a hotel in Marmaris, Dogan news agency reported."I await all the people in the airports, the squares and the streets," said Erdogan."Our nation can be calm. Our Prime Minister [Binali Yildirim] has made the necessary announcements."A presidential source said Erdogan was in a secure location as per government protocol.Meanwhile, The Associated Press reported on Saturday that loud explosions had been heard in Turkey's capital Ankara and CNN-Turk reports an explosion occurred at the state-run television building.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.Dozen of tanks were seen moving toward a palace that is now used by the prime minister and deputy prime ministers. A civilian car tried to stop one of the tanks, but it rammed through the vehicle as those in the car escaped.Erdogan has faced down significant challenges before including the 2013 wave of protests against his rule and has also cracked down on followers of his arch-enemy Fethullah Gulen.Elected on a wave of popular support, in particular from conservative and pious Muslim voters, Erdogan has dominated Turkish politics since he first become premier in 2003.He took the office of president in 2014 polls and if he seeks a second mandate could in theory stay in power until 2024.