"An Israeli Saar warship entered Lebanese territorial waters at 7:30 am (0530 GMT) yesterday morning before being intercepted by the Italian navy's Bettica, which is part of UNIFIL," an army spokesman told AFP.

The Israeli vessel travelled three miles (about five kilometres) before leaving , according to an army statement.

Israeli jets regularly violate Lebanese airspace, but it is rare for warships to enter Lebanese territorial waters.

Yasmina Bouziane, spokeswoman for the UN Interim Force in Lebanon (UNIFIL), and said an investigation was underway.

"We received a report saying that a ship coming from Israel entered the maritime area of operation without proper procedures, violating Lebanese territorial waters," she said.

"UNIFIL is investigating this issue and UNIFIL command has contacted the IDF (Israeli Defence Forces)."

The overflights have drawn criticism from Lebanese authorities and the international community as they are in violation of UN resolution 1701, which ended the 2006 war between the militant group Hezbollah and Israel.

Tensions have risen along the Lebanese-Israeli border since a declaration of "open war" by Hezbollah chief Hassan Nasrallah after the February assassination of top Hezbollah operative Imad Mughniyeh in Damascus.

Hezbollah has blamed Israel for the killing, but it denies any involvement.

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