TEL AVIV, March 13 (Reuters) - Israel's air defences could fend off long-range ballistic missiles of the kind deployed by Iran and Syria but the Jewish state remains vulnerable to cruise missiles, an Israeli newspaper reported on Thursday.

Long-running tensions between Israel and arch-foe Iran over the latter's nuclear programme have stirred regional war fears, with both countries at times flexing their military muscle. Israel, which is widely assumed to have the Middle East's only atomic arsenal, designed its most advanced air defence system, Arrow II, around a doctrine of spotting and shooting down Iranian Shehab or Syrian Scud missiles at high altitudes.

But Maariv daily said Israel remains unprepared for enemy cruise missiles, which fly at ground-hugging heights to dodge radar and can in theory be used for sneak nuclear strikes.

Israel's Defence Ministry denied the Maariv report.

Ukraine said in 2005 that several Soviet-era X-55 cruise missiles had been "smuggled" out of its territory to Iran. Also known as Kh-55s or AS-15s, the missiles have a range of 3,000 km (1,800 miles) -- more than enough to reach Israel from Iran.

According to Maariv, Israeli experts believe Iran may have used the X-55s as models for a line of locally designed cruise missiles. Iran, which denies Western allegations that it seeks nuclear weapons, has not given details on any cruise missile programme and describes its armed forces as defensive only.

Syria is not known to have cruise missiles.

Shlomo Dror, spokesman for Israel's Defence Ministry, said Israel has a "response" for any cruise missile attack.

Complementing Arrow II for lower-altitude threats are U.S.-supplied Patriot and Hawk batteries, both of which have radars that could spot cruise missiles, according to Dror.

"Israel has also been working on more up-to-date countermeasures," Dror said without elaborating.

The United States turned down Israeli requests in the 1990s to buy its Tomahawk cruise missiles. Israel is reported to have tried to develop its own cruise missiles since. (Additional reporting by Ronald Popeski in Kiev; Writing by Dan Williams; Editing by Catherine Evans)

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