(Adds U.S. State Department comment)
* Palestinians not widely supportive of al Qaeda
* Alleged plot involved bombers posing as tourists
* U.S. Embassy listed among targets
* Hamas rejects report as "silly fabrications"
By Dan Williams
JERUSALEM, Jan 22 (Reuters) - Israel said on Wednesday it had arrested two Palestinians from East Jerusalem who were planning to carry out attacks for al Qaeda, including on the U.S. Embassy, with the help of foreign suicide bombers posing as Russian tourists.
The men were recruited by another al Qaeda agent in the Gaza Strip, said Israel's Shin Bet intelligence agency, the second Israeli report in as many months suggesting the militant network was taking root among Palestinians.
Hamas Islamists governing Gaza rejected the spy agency's account as "silly fabrications", saying it was an attempt to justify Israeli military strikes in the Palestinian territory.
Security experts say al Qaeda and its global agenda have had only a fringe appeal among Palestinians as they pursue a more nationalist conflict with Israel.
Shin Bet said the two Palestinians planned to provide bomb vests to foreign militants posing as Russian tourists for attacks on an Israeli convention centre in Jerusalem and the U.S. Embassy in Tel Aviv. It said they also planned to kidnap a soldier and attack an Israeli bus in the occupied West Bank.
The pair, who could travel freely in Israel because of their Jerusalem residency, were recruited over Facebook and Skype, Shin Bet said in a statement. It said one of the men was arrested as he prepared to travel to Syria, via Turkey, to undergo weapons training.
Shin Bet did not say if the Palestinians had lawyers or how they might plead in open court. Civil rights groups have often accused the Shin Bet of using duress against terrorism suspects.
U.S. State Department spokeswoman Marie Harf said: "Obviously we have been in contact with the Israeli government regarding these threats... The U.S. Embassy was not just the target, but other targets were mentioned, I believe."
Israel captured East Jerusalem, along with the West Bank and Gaza Strip, in the 1967 war. It annexed East Jerusalem as its capital - a move not recognised abroad - and says it may cede West Bank territory to the U.S.-backed Palestinian Authority (PA). It quit Gaza in 2005, leading to Hamas's rise there.
The Shin Bet said a third Palestinian, from the West Bank city of Jenin, was in custody on suspicion of planning to set up an al Qaeda cell in his area. Two of the detainees were arrested last month and the third this month, it said.
In November, Israeli troops said they had killed three Palestinian militants linked to al Qaeda in a West Bank clash. The al Qaeda-inspired Majles Shura al-Mujahideen (Holy Warriors' Assembly) claimed the slain men as its own. The PA sought to play down the link.
The Shin Bet said al Qaeda's spread in the West Bank was "still at its inception, and possible to stop".
Citing the alleged recruitment work by al Qaeda in Gaza, the Shin Bet accused Hamas authorities of "allowing Salafis to carry out terrorism as long as it is not against them".
Hamas spokesman Sami Abu Zuhri said Israel was seeking a pretext for its attacks in Gaza. Earlier on Wednesday, an Israeli air strike killed a militant from the Palestinian faction Islamic Jihad blamed for a cross-border rocket salvo last week.
Abu Zuhri said the Shin Bet statement was "silly fabrications," adding: "Facebook is not a Hamas network."
Hamas, while hostile to Israel, has often observed Egyptian-mediated truces with it and curbed more radical Salafi Muslims aligned with al Qaeda. (Writing by Dan Williams; Additional reporting by Nidal al-Mughrabi in Gaza and David Brunnstrom in Washington; Editing by Janet Lawrence)