Greek Prime Minister George Papandreou condemned on Monday evening the Israeli military operation against a flotilla carrying humanitarian aid to Gaza. 'Today's tragic events are unacceptable. Violence used during the operation cannot be justified,' Papandreou said. Expressing condolences to the families of the victims, the Greek leader noted there were no Greek activists among the casualties. He said Greece is asking Israel for their quick return to Greece. 'Israel's security and the security of the wider area, as well as solutions to the problems, can be served only through negotiations and UN Security Council resolutions,' stressed Papandreou. The Greek premier held a series of telephone conversations over the past few hours with Palestinian President Mahmoud Abbas, President of Cyprus Demetris Christofias, Turkish Prime Minister Recep Tayyip Erdogan, Israeli Foreign Minister Avigdor Lieberman and General Secretary of the Arab League Amr Moussa. Greece suspended a scheduled visit by Israel's air force commander due in Athens on Monday and canceled an ongoing joint air exercise with Israel. 