Turkey and Greece have announced rival naval exercises in the east Mediterranean for Tuesday, amid rising tensions over claims to oil and gas in the region. The discovery of major deposits in waters surrounding Cyprus and the Greek island of Crete triggered a scramble for energy riches and revived old regional rivalries. Tensions flared earlier this month, when Turkey sent a research vessel into disputed waters, accompanied by warships. Greece and its EU ally France both dispatched their own naval assets to the area to monitor Turkey's work. Germany says it's sending its foreign minister to Athens and Ankara on Tuesday to help resolve the issue.