TEL AVIV, Nov 21 (Dan Williams/Reuters) - Israel has gradually boosted naval patrols around its east Mediterranean natural gas fields for fear of guerrilla attacks and as maritime rivalry with Turkey deepens, an Israeli official said on Monday.

Missile boats have stepped up missions around the Tamar and Leviathan platforms over the past year, as well as coordination with private security firms contracted by the U.S.-Israeli exploration consortium, the official said.

We have replicated the arrangements already in place at Yam Tethys, the official said, referring to another Israeli gas field 40 km (25 miles) off southern Ashkelon port, near the waters of the Palestinian territory Gaza.

Tamar and Leviathan, in which Israel sees a potential pipeline to energy independence, are around twice and three times as far out to sea, respectively. That challenges Israel's small navy, which is more accustomed to close coastal patrols.

The Israeli military's newspaper Bamahane said the navy was undergoing expansion including the appointment of a commodore to handle the induction of two more German-made submarines and address the new need to protect the drilling rigs.

Bamahane did not elaborate, but experts have long voiced concern that Tamar and Leviathan could be targeted by Lebanese Hezbollah guerrillas given Beirut's complaints at what it deems Israel's unilateral exploration in the absence of an agreed maritime border. The two countries are technically at war.


MISSILES

One danger is a proximity attack, by frogmen, by boats, by terrorists in some fashion, Giora Eiland, a former Israeli national security adviser, told the Globes business journal in May.

Another, bigger challenge is how to face the threat of missiles, because today you can launch missiles from tens of kilometres away, he said.

Israel and Cyprus, which is doing its own drilling for eastern Mediterranean gas in consortium with Texas-based Noble Energy, are also mindful of Turkey's naval assertiveness in the area.

NATO-member Turkey, which pledged in September to send in more frigates and torpedo boats, says any natural resources found off Cyprus should be shared with the island's breakaway ethnic-Turkish north, a state recognized solely by Ankara.

Turkey's Islamist-rooted government also described the naval reinforcements as a precaution against Israel intercepting pro-Palestinian sympathizers who attempt to sail to blockaded Gaza, as it did in 2010, killing nine Turks.

The Israeli official confirmed that the new safeguards around Tamar and Leviathan came in response to the perceived Hezbollah threat, but was more circumspect about the face-off with Turkey, formerly Israel's stalwart Muslim ally.

We are keeping up with all the challenges of operating in the eastern Mediterranean, the official said.

Tamar and Leviathan, from which Israel predicts at least $150 billion in gas revenues, are scheduled to begin pumping in 2013 and 2017 respectively. Yam Tethys is currently Israel's only working rig.