Turkey says waters off the coast of war-divided Cyprus where Greek Cypriots plan to explore for natural gas lie within its continental shelf, sharpening multi-sided disputes over major fields under the eastern Mediterranean.

Ankara has warned international companies bidding for drilling rights in the area that it will not allow any outside exploration in the disputed waters that are internationally acknowledged as belonging to the Greek Cypriot government in Nicosia.

Total of France, Italy's Eni, Novatec of Russia, Delek of Israel and Malaysia's state oil company Petronas are among the 15 international companies and consortia seeking licenses to drill off southern Cyprus in the face of Ankara's strident objections.

The Greek Cypriot government in Nicosia is currently assessing the bids. It is not yet clear how seriously the companies concerned are taking the Turkish warnings to back off.

Cyprus has been divided since Turkey invaded in 1974 and seized the northern one-third of the island. It proclaimed that zone the Turkish Republic of Northern Cyprus.

Only Ankara recognizes the TRNC, where 30,000 Turkish troops are stationed. The Greek Cypriot government is internationally recognized.

The Greek Cypriots have already begin exploration in Block 12, which abuts the large Leviathan field discovered in Israeli waters in 2110 and is considered to be an extension of that field.

Leviathan contains some 20 trillion cubic feet of gas and the Cypriots' Block 12, known as the Aphrodite field, is believed to hold similar volumes.

All told Israel has found gas reserves of around 25 tcf to 30 tcf, and more strikes are expected. It plans to co-produce with the Greek Cypriots then jointly export their gas to the European Union via Greece.

The U.S. Geological Survey reported in 2010 that the Levant Basin contains 122 tcf and 4 billion barrels of oil, enough to transform the economies of Israel, Cyprus, Lebanon and Syria.

"The recent discoveries of natural gas under the Eastern Mediterranean seabed have seemingly prompted Ankara to renew its diplomatic campaign on behalf of Turkish Cypriots," observed Simon Henderson of the Washington Institute for Near East Policy.

Turkish Prime Minister Recep Tayyip Erdogan declared in September 2011: "Turkey, as a guarantor of the Turkish Republic of Northern Cyprus, has taken steps in the area (of the offshore fields) and it will decisively pursue its right to monitor international waters in the east Mediterranean."

This has thrust Turkey into confrontation with the Greek Cypriots and Israel, and could eventually affect Lebanon, Syria and Egypt as well.

Ankara's fury with the Greek Cypriots is likely to intensify in July, when Cyprus takes over the rotating presidency of the European Union for six months.

Lebanon, widely believed to sitting on gas fields as extensive as those found by Israel and, it appears, by Cyprus as well, is challenging the maritime zone declared by Israel.

Iran and its Lebanese proxy, Hezbollah, have accused Israel of plundering Lebanon's offshore energy assets. Hezbollah has warned it will take military action, if necessary, to prevent that.

"Ankara, already sympathetic to Hezbollah, may be tempted to take sides in this dispute despite concerns about Lebanon exploiting its own offshore resources," cautioned Henderson.

The Lebanese government plans to hold a high-level meeting in Beirut with potential investors regarding its offshore prospects in July to accelerate exploration operations off its shores.

This is likely to deepen the dispute between Lebanon and Israel, its southern neighbor with whom it is technically still at war.

Hezbollah fought Israel's military forces to a standstill in a 34-day war in July-August 2006, and many in both countries consider that unfinished business.

Israel and Egypt already have maritime border agreements with Cyprus, but Lebanon has not.

Beirut disagrees with Israel's accord, but will have to find some accommodation with the island before it starts any exploratory drilling.

Henderson observed that strife-torn Syria, "as an oil and gas producer … is expected to look offshore for reserves at some point in the future."

But Turkey, its onetime ally, is now firmly behind opposition forces seeking the downfall of President Bashar al-Assad's regime.

The two countries are at odds over the Turkish province of Hatay, which Damascus claims.

So the already complex multi-sided dispute over the riches of the eastern Mediterranean could get even more complicated.