TEL AVIV, Aug 24 (Reuters) - Israeli Prime Minister Benjamin Netanyahu said on Monday that Iran had tried to kill one of his sons, but gave no details about when the alleged plot took place, which son was targeted or how close it came to being carried out.

Netanyahu's allegation underscores the heightened tensions since the U.S.-Israeli war on Iran began in February, during which Supreme Leader Ayatollah Ali Khamenei and other senior Iranian leaders were killed.

Netanyahu, whose coalition is trailing in opinion polls two months before an October 27 general election, made the claim in a telephone interview with Israel's Channel 14. He was responding to reports that one of Israel's security agencies had refused to provide protection for a political rival ahead of the nationwide vote.

"As for my sons. Here, I think there is something quite unbelievable, yes. Iran targeted one of my sons. Iran tried to kill, to murder one of my sons," Netanyahu told the conservative channel known for its favourable coverage of the government.

"Iran tried to murder one of my sons, and therefore this security protection is not a luxury," he said, without providing any further details about the alleged plot or how close it came to being carried out.

It was not immediately clear which of his sons he was referring to. Netanyahu's elder son, Yair, lives in Miami.

Iran's mission at the United Nations in New York did not immediately respond to a request for comment on the accusation.

Netanyahu also said he had told the Shin Bet security agency chief David Zini that appropriate security should be provided for any prime ministerial candidate.

Israeli media had reported earlier that Zini declined to provide security for Gadi Eisenkot and told the country's election authority there was no plot to harm him.

Eisenkot's party is projected to win the largest number of seats in the election, although Israeli governments are usually formed through coalitions among multiple parties rather than by a single party winning a parliamentary majority outright.

(Reporting by Andreea Popescu and Alexander Cornwell; Editing by Howard Goller)