JERUSALEM (Reuters) - Israel sounded the all-clear on Tuesday after a bomb threat led France, Switzerland and Bulgaria to scramble warplanes to escort an El Al Boeing 747 as it overflew their territory from New York to Tel Aviv.

The passenger jet landed without incident and no bomb was found on board, an Israeli security official said, adding that Israel had previously determined that the scare was bogus and required no unusual measures by the flight crew.

After the plane departed New York, a U.S.-based El Al security officer received word of a person who had telephoned to say a bomb would go off on board in an hour, and a second call was later received by Israeli authorities, the official said.

"We ran our own checks and understood that the threat was not serious," said the official, who declined to elaborate on the calls other than to say that they sounded like they were made by a person who was trying to obscure his or her voice.

The Swiss Air Force said it had deployed an air police "hot mission" to accompany a flight. Israeli media aired a photograph, apparently taken by an El Al passenger through a window, of a Swiss F-18 a few dozen meters (yards) to starboard.

Sky Guide, a Swiss air navigation service provider, said the bomb threat was received when the El Al jet was over France. It said the flight was escorted by French warplanes before it crossed into Swiss airspace.

Bulgaria also sent jet fighters to escort the Israeli airliner over its territory, the defense ministry in Sofia said, calling this a response to suspicions about a bomb on board.

El Al, Israel's flag carrier, is considered one of the most security-conscious in the world. The Israeli official suggested the European countries' response to the scare was excessive.

"We did not see a threat, and it seems that they took action after receiving word of the alert separately, perhaps from the United States," the official told Reuters.

(Reporting by Dan Williams, Tova Cohen and Tsvetelia Tsolova; Writing by Jeffrey Heller; editing by Ralph Boulton)