Greek Prime Minister Alexis Tsipras arrives at the Auberge de Castille for the Southern EU Countries Summit in Valletta, Malta June 14, 2019. REUTERS/Darrin Zammit Lupi

ATHENS (Reuters) - Greece and Cyprus will push their EU partners to penalize Turkey, including the possible option of sanctions, if Ankara is verified to have started drilling for gas west of Cyprus, Greek Prime Minister Alexis Tsipras said on Sunday.

The discovery of lucrative energy reserves in the eastern Mediterranean has drawn into sharper focus long-standing tensions between Turkey and the Greek Cypriot government.

A Turkish drill ship has been anchored west of Cyprus since May. Cyprus and Greece say the vessel is encroaching into Cyprus’s exclusive economic zone (EEZ) - an area which Cyprus can use for commercial exploitation. Turkey says the area is on its continental shelf.

“We have agreed .. to prepare the ground in the coming week that the (European Union) summit take the relevant decisions, even sanctions against Turkey, if it is verified that there has been a drill (by Turkey) in the Cypriot EEZ,” Tsipras told reporters.

Greece is a close ally of the government in Nicosia and also has its own decades-old disputes with neighboring Turkey on issues relating to airspace in the Aegean Sea, and mineral rights in the same region.

Cyprus first discovered offshore gas reserves in 2011, which led to other discoveries. Turkey says any natural resources around the ethnically-split island also belong to Turkish Cypriots. They proclaimed their own independent state in 1983, but were founding partners of the Cypriot republic established after independence from Britain in 1960.

The east Mediterranean island was split in a Turkish invasion in 1974 triggered by a brief coup orchestrated by the military junta then ruling Greece. Relations between the Greek and Turkish Cypriot communities have festered since 1963, when a power-sharing agreement crumbled amid violence.