Turkey has begun drilling for oil and gas onshore in northern Cyprus despite protests from the Republic of Cyprus that the action is illegal.
The state Turkish Petroleum Corporation (TPAO) began drilling at a 3,000m (9,840ft) deep well near the town of Trikomo (Iskele in Turkish).
The launch ceremony was attended by Turkish Energy Minister Taner Yildiz.
Turkey was outraged last year when Cyprus allowed Texas-based Noble Energy to explore for natural gas offshore.
However, the Republic of Cyprus is an internationally recognised state, unlike the Turkish-controlled north which broke away during the Turkish invasion of 1974.
It is badly in need of income and energy.
Ankara argues that until the ongoing talks to reunite the island succeed, no government has the right to negotiate over Cyprus's territorial waters.
'Force for peace'
Mr Yildiz said the Turkyurdu-1 well could be "a force for peace in Cyprus".
"While energy has produced wars in other parts of the world, here it will be a force for peace," he said.
TPAO is expected to carry out exploratory drills for between three and six months, AFP news agency reports.
A spokesman for the Cypriot government, which Turkey does not recognise, said: "Turkey and the Turkish Cypriot leadership are violating the law by going ahead with drilling."
In Athens, a spokesman for the Greek foreign ministry also said the action was illegal and in contravention of UN resolutions on the island calling on member states to respect the sovereignty, independence and territorial integrity of Cyprus.
"This action once again highlights that the Cyprus issue is primarily an issue of invasion and occupation," the Greek spokesman was quoted as saying by Reuters.