A joint declaration at a Balkan summit in Istanbul on Wednesday says: "We deplore the loss of life and injuries during the incident in international waters," in the eastern Mediterranean on May 31. The raid left eight Turks and one Turkish American dead.

The countries say they want "an impartial, independent and internationally credible investigation on this matter."

They stress the urgent need to improve the humanitarian situation in Gaza, saying they expect announcements from Israel on easing the blockade of Gaza to be quickly followed by "concrete measures" with immediate positive impact on the lives of the people of Gaza.