Bulgarian investigators worked with the FBI and Interpol Thursday to identify the suicide attacker behind a deadly bombing on a bus carrying Israeli tourists, as Israeli Premier Benjamin Netanyahu said the attack "was perpetrated by Hizbullah" and Iran denied involvement.

The attack "was perpetrated by Hizbullah, Iran's leading terrorist proxy," said Netanyahu, describing the Lebanese group as "the long arm of Iran."

U.S. defense officials have held talks with their Israeli counterparts over whether Israel might strike at Syria's weapons facilities as its regime faces possible collapse, the New York Times reported.

The Times on Wednesday cited officials as saying that the Pentagon is not advocating military action because it feels that such an attack would help Syrian President Bashar Assad rally support against foreign intervention.

Bulgaria said Thursday a suicide bomber dressed as a tourist and with fake U.S. ID was behind an attack on Israelis on the Black Sea that killed seven people and left two in a coma.

U.S. President Barack Obama called the attack on a bus at Burgas airport on Wednesday, the deadliest against Israelis abroad since 2004, a "barbaric terrorist attack."

Israel expressed concern on Thursday that Hizbullah might attempt to transfer advanced weapons systems or chemical weapons from Syrian to Lebanon if the regime of President Bashar Assad collapsed.

"We are vigilantly watching the developments and the possibility that Hizbullah might attempt to transfer advanced weapons systems or chemical weapons from Syria to Lebanon,” Israeli Defense Minister Ehud Barak said in a statement issued by his office.

Israel accused Iran on Wednesday of being behind a deadly attack against Israeli tourists at an airport in Bulgaria, which Sofia said killed seven people and wounded more than 30 others.

There was no immediate confirmation of the nationalities of the casualties, but Israel's foreign ministry said the blast had targeted a bus carrying Israeli tourists who had just landed at the port city of Burgas on the Black Sea.

Avigdor Lieberman, whose ultra-nationalist Yisrael Beitenu is a key member of Israel's ruling coalition, on Wednesday said he had no intention of leaving government a day after the Kadima party withdrew.

Despite differences with Israeli Prime Minister Benjamin Netanyahu over plans to expand the military conscription law to include more ultra-Orthodox Jews, Lieberman, who is also foreign minister, said he had no intention of quitting the coalition.

Members of Israel's center-right Kadima party decided on Tuesday to leave Prime Minister Benjamin Netanyahu's coalition after the sides failed to agree on a new universal draft law.

A vast majority of the party led by Shaul Mofaz was in favor of leaving the coalition after only joining it in May, reducing the governing coalition by 28 members but still leaving it with a majority.

Syrian President Bashar Assad has moved army forces from the Golan Heights area next to Israel toward Damascus and other internal conflict zones, the Israeli army intelligence chief said on Tuesday.

As fighting rages between Assad's forces and rebels trying to oust his government, he has moved troops from the Syrian side of the disengagement line that divides the Golan Heights between Syria and Israeli-held territory, he said.

Israeli police said they have arrested a Jewish man suspected of spray painting death threats outside the Jerusalem home of a prominent Israeli anti-settlement activist working for Peace Now.

"A 21-year-old man suspected of spraying the graffiti on Hagit Ofran's home was arrested on Monday evening, following the incident earlier that day," police spokesman Micky Rosenfeld told Agence France Presse.

U.S. Secretary of State Hillary Clinton on Monday said Washington would use "all elements of its power" to prevent Iran going nuclear and was working in "close consultation" with Israel over how to do so.

Speaking to reporters at the end of a whirlwind 24-hour visit to Jerusalem, Clinton said that Iran not yet decided to curb its nuclear ambitions, and warned that Washington would stop at nothing to prevent it from getting a nuclear bomb.