The US House of Representatives passed a resolution on Tuesday officially recognising the "Armenian genocide", a symbolic but unprecedented move that angered Turkey amid already heightened tensions with Washington.

Cheers and applause erupted when the chamber voted 405 to 11 in support of the measure "affirming the United States record on the Armenian Genocide", a first for the US Congress, where similar measures with such direct language have been introduced for decades but never passed.

US lawmakers delivered a two-punch rebuke to Turkey on its national day, with the genocide measure passing alongside a bill that imposes sanctions over Ankara's assault on Kurdish-controlled territory in northeastern Syria that was made possible by the withdrawal of American troops.

House Speaker Nancy Pelosi said she was honored to join her colleagues "in solemn remembrance of one of the great atrocities of the 20th century: the systematic murder of more than 1.5 million Armenian men, women and children by the Ottoman Empire."

The Armenians say the mass killings of their people from 1915 to 1917 amounted to genocide, a claim recognised by some 30 countries.

Turkey strongly denies the accusation of genocide and says that both Armenians and Turks died as a result of the First World War. It puts the death toll in the hundreds of thousands.

Ankara reacted swiftly, rejecting the House's recognition as a "meaningless political step" and warning it risks harming ties "at an extremely fragile time" for international and regional security.

"We believe that American friends of Turkey who support the continuation of the alliance and friendly relations will question this grave mistake and those who are responsible will be judged by the conscience of the American people," Turkey's foreign ministry said in a statement.

But Armenia's Prime Minister Nikol Pashinyan hailed the House move, tweeting that it was a "bold step towards serving truth and historical #justice that also offers comfort to millions of descendants of the Armenian Genocide survivors".

'Never again'

In 2017, newly inaugurated US President Donald Trump criticised the killings as "one of the worst mass atrocities of the 20th century" but in keeping with longstanding US practice, he stopped short of using the word genocide.

Before being elected in 2008, Trump's predecessor Barack Obama had pledged to recognise the genocide, but ultimately did not do so during his two terms in office.

But Pelosi, the top Democrat in Congress, delivered bold remarks to the House on Tuesday, saying the truth of the "staggering crime" has been denied too often.

"Today, let us clearly state the facts on the floor of this House to be etched forever into the Congressional Record: The barbarism committed against the Armenian people was a genocide."

The House also passed a bipartisan measure that imposes sanctions on senior Turkish officials involved in the decision to launch the country's invasion of Syria and a Turkish bank with ties to President Recep Tayyip Erdogan, and requires the Trump administration to penalize Turkey's procurement of a Russian-made missile-defense system.

A similar sanctions bill was introduced in the Senate, but no vote has been taken.

Turkey's foreign ministry "strongly condemned" the House decision to approve the sanctions, saying it did "not bode well with the spirit of relations" as NATO allies and also went against the deal reached with the United States over Syria.

The Trump administration had previously announced more modest punitive measures on Turkey for the invasion, before lifting them when it negotiated a ceasefire with Ankara.

Former vice president Joe Biden, a 2020 Democratic White House hopeful, praised the Armenia vote, tweeting that "by acknowledging this genocide we honor the memory of its victims and vow: never again."

It was also welcomed outside the political realm. US television reality star Kim Kardashian, who has Armenian ancestry, tweeted about the vote to her 62 million followers.

"This is personal for me, and millions of Armenians who descended from genocide survivors," she said.

According to estimates, there are between 500,000 and 1.5 million Americans of Armenian origin.