ANKARA, Turkey - Turkey summoned the ambassador from the United States on Friday to protest the U.S. Senate’s approval of a resolution that recognizes as genocide the mass killings of Armenians by Ottoman Turks a century ago, an official said.

U.S. Ambassador David Satterfield was summoned to the Turkish Foreign Ministry, where Deputy Foreign Minister Sedat Oney conveyed Turkey’s “strong reaction” to the Senate action, a ministry official said.

The official provided the information on condition of anonymity in line with government protocol.

The Senate’s unanimous vote on Thursday drew angry denunciations from Turkish leaders and accusations that Washington was undermining relations with a key NATO ally.

Historians estimate that up to 1.5 million Armenians were killed around World War I, a mass loss of life that many scholars regard as the 20th century’s first genocide. Turkey disputes the description, saying the death toll was inflated and those killed were victims of a civil war.

Turkey has called for a joint committee of historians to investigate the slayings.

The Senate resolution was blocked three times at the request of the White House before it passed Thursday. The Senate vote follows a vote by a Senate committee to impose sanctions on Turkey over its offensive in Syria and purchase of a Russian S-400 missile system.