ANKARA: Turkey Tuesday voiced “deep regret”over US President Barack Obama's description of the massacre of Armenians as “one of the worst atrocities of the 20th century,” saying it was biased.

“We find the statement that distorts historical facts as very problematic in every respect and deeply regret it,” the foreign ministry said in a written statement.

In an annual message commemorating the World War I massacre of Armenians by Ottoman Turks, Obama Tuesday called for “a full, frank, and just acknowledgment of the facts” of the “brutal” killings.

While denouncing the massacre of 97 years Obama did not use the term “genocide,” but he implicitly called on Turkey to acknowledge the role played by the Ottoman Empire.

The foreign ministry said such “one-sided statements” were complicating efforts to normalise ties between neighbours Turkey and Armenia.

“We expect an important ally like the United States not to deepen the problem by adopting an approach harming Turkish-Armenian relations, but to contribute to a solution in a constructive manner,” said the ministry.

Armenians say up to 1.5 million people were killed during World War I as the Ottoman Empire was falling apart.

Turkey denies a genocide occurred and says up to 500,000 Armenians and at least as many Turks died in civil strife when Armenians rose against their Ottoman rulers and sided with invading Russian troops.