Turkish Foreign Minister Abdullah Gul Thursday denounced as "unacceptable" a resolution by the Slovak parliament recognising the 1915 massacre under the Ottoman empire of hundreds of thousands of Armenians as genocide.

On Tuesday, the Slovak parliament adopted a resolution saying: "The Slovak parliament recognises the genocide of Armenians in 1915 during which hundreds of thousands of Armenians in the Ottoman Empire were killed and considers this act a crime against humanity."

But Gul also sought to downplay the issue, saying the initiative was spearheaded by the Slovak opposition and not the government.

The resolution was adopted in the same session as another one giving the green light to opening negotiations on Turkey's accession to the European Union but were voted on separately, Slovak parliament spokesman Michal Dyttert said.

"This is unacceptable... We will take the necessary (diplomatic) steps," Gul told reporters, but declined to elaborate.

"I think this development is the result of (Slovak) domestic politics. Opposition parties sometimes behave irresponsibly... The Slovak government did not support it," he said.

The Turkish foreign ministry issued a strongly worded statement, blaming the Slovak resolution on "a fait accompli by one political party (to) accept as genocide the tragic events of 1915."

"Passing judgment on the contested periods of another's history cannot be among the duties and responsibilities of national parliaments," it said.

"It is clear that this decision, taken for political profit by distorting events that took place under the conditions of World War I and caused great suffering to Turks and Armenians alike, does not constitute a responsible course of action," the statement said.

The massacres of Armenians during World War I is one of the most controversial episodes in Turkish history.

Armenians say up to 1.5 million of their kinsmen were massacred in orchestrated killings nine decades ago.

Turkey categorically rejects any claims of genocide and says that 300,000 Armenians and thousands of Turks were killed in what was civil strife during the dissolution years of the Ottoman Empire when rebellious Armenians sided with invading Russian troops.

Ankara is also under pressure from the EU, which it is seeking to join, to establish diplomatic relations with Armenia.

In 2001, France triggered a storm in its relations with Turkey when its parliament passed a law acknowledging the massacres as genocide.

Ankara retaliated by sidelining French companies from public tenders and cancelled several projects awarded to French firms.