The US House of Representatives voted 405-11 in favor of a resolution recognizing the mass killings of Armenians a century ago as a genocide.

The resolution recognizing the 1915-1923 massacre of an estimated 1.5 million Armenians as a genocide is being seen as a strong rebuke against the government of Turkey - the Ottoman Empire’s successor state - and its president, Recep Tayyip Erdogan, who has long lobbied against such moves.

Turkish Foreign Minister Mevlut Cavusoglu slammed the move saying the decision was “null and void.” In a tweet, Cavusoglu said Turkey had thwarted a “big game” with its offensive into northeastern Syria and that the move by the House was aimed at taking revenge for the operation.

“This vote sends a clear message to Erdogan that America will no longer turn a blind eye to Ankara’s atrocities. This is especially timely today, as Turkey commits new crimes against our Kurdish allies and at-risk Christian and Yezidi civilians across northern Syria,” said Aram Hamparian, the Executive Director of the Armenian National Committee of America (ANCA) in a press release statement.

According to a Reuters report, the nature and scale of the killings remain highly contentious nearly a century after they took place. Turkey accepts that many Armenians died in partisan fighting beginning in 1915, but denies that up to 1.5 million were killed and that this constituted an act of genocide – a term used by many Western historians and foreign parliaments.

Barack Obama, the former US president, was criticized in 2015 for stopping short of calling the 1915 massacre of Armenians a genocide, prompting anger and disappointment from those who have been pushing him to fulfill a campaign promise and use the politically fraught term on the 100th anniversary of the killings in April of that year.