After a decades-long campaign to get the U.S. to formally recognize the Armenian genocide, the U.S. House of Representatives voted overwhelmingly on October 29 to recognize the mass killings of Armenians a century ago as a genocide, a symbolic but historic vote instantly denounced by Turkey.

The Democratic-controlled House voted 405-11 in favor of a resolution asserting that it is U.S. policy to commemorate as genocide the killing of 1.5 million Armenians by the Ottoman Empire from 1915 to 1923, according to Reuters.

The vote reportedly marked the first time in 35 years that such legislation was considered in the full House, underscoring widespread frustration in Congress with the Turkish government, from both Democrats and President Donald Trump’s fellow Republicans.

While it is nearly universally acknowledged that the Ottoman Empire committed the genocide against Armenians starting in 1915, Turkey has vigorously opposed labeling the events as such. During the Cold War, Ankara was one of the U.S.’s closest allies and it has in the past been able to use its clout in Washington to block any attempts at formal genocide recognition.

Shortly after the Armenian genocide vote, House lawmakers from both parties also overwhelmingly backed legislation calling on Trump to impose sanctions on Turkey over its offensive in northern Syria, another action likely to inflame relations with NATO ally Turkey.

Meanwhile, Turkey says US House's decision to call the 20th-century Armenian killings 'genocide' has no historical or legal basis.

Turkey rejected the US House of Representatives' official recognition of the "Armenian genocide" a century ago, warning it risks harming ties "at an extremely fragile time" for international and regional security. 

"The resolution which has apparently been drafted and issued for domestic consumption is devoid of any historical or legal basis," Turkey's Foreign Ministry said in a statement after the vote.