Biden says Armenian mass killing was genocide

Joe Biden has become the first US president to issue a statement formally describing the 1915 massacre of Armenians as a genocide.

The killings took place in the waning days of the Ottoman Empire, the forerunner of modern-day Turkey.

But the issue is highly sensitive, with Turkey acknowledging atrocities but rejecting the term "genocide".

Foreign Minister Mevlut Cavusoglu said on Saturday that Turkey "entirely rejects" the US decision.

"We will not take lessons from anyone on our history," he tweeted.

Later the Turkish foreign ministry said it had summoned the US ambassador to convey Ankara's "strong reaction".

Previous US administrations have not used the term genocide in formal statements amid concerns over damaging relations with Turkey, a Nato ally.