*Contributed reporting

ANKARA, Turkey — The Turkish capital was rocked by violent clashes overnight as the government fought back against a military coup, but authorities said Saturday they had managed to stave off a rebellion that has plunged one of the United States’ most important NATO allies into chaos.

Turkish President Recep Tayyip Erdogan on Saturday called the coup attempt “an act of treason,” and Turkey’s army chief of staff said the plot was carried out by a militant faction within the armed forces.

”Turkey has a democratically elected government and president. We are in charge and we will continue exercising our powers until the end,” Erdogan said after landing in Istanbul.

READ MORE: After a night of clashes, Turkish president asserts that military coup has been defeated