An attack was made on an ethnic Greek journalist who runs a minority newspaper in Turkey.
Andreas Rombopulos, who runs the newspaper Iho, or Echo, was attacked and beaten by two people outside the paper's offices in the city center. He was being treated at a local hospital for head and arm injuries, but was not in a life-threatening condition, authorities said.
Istanbul is home to a dwindling Greek minority of about 3,000 people, down from an estimated million at the turn of the century.
Greek Foreign Ministry spokesman Giorgos Koumoutsakos said Rombopulos was "brutally attacked."
"At a time when efforts are being made and steps are being taken to further improve and reinforce relations between the two countries, some people, with their unacceptable and criminal acts, are trying to create obstacles," Koumoutsakos said. "They will not succeed."
"We unreservedly condemn them," Koumoutsakos said, adding that Greece expected Turkish authorities to arrest and try the perpetrators and to take measures so that such attacks are not repeated.
In January, ethnic Armenian journalist Hrant Dink was shot dead in front of his newspaper's office in a brazen daylight attack that prompted international condemnation and debate within Turkey about free speech.
Traditional rivals Greece and Turkey have been improving ties recently. On Tuesday, they announced they were expanding military cooperation as part of new confidence-building measures. Greek Prime Minister Costas Karamanlis is expected to visit to Turkey in the near future for what would be the first official visit by a Greek premier in 48 years.