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.

The United States moved to freeze the assets of dozens of Syrian ministers Wednesday, piling pressure on the regime as it reeled from a bomb attack that took out three core security officials.

The White House insisted President Bashar Assad was "losing control" of power, as Washington marshaled its forces to push the regime toward its tipping point.

Arab foreign ministers are to hold an emergency meeting on Sunday on the crisis in Syria, Arab League chief Nabil al-Arabi said, after a Damascus bombing on Wednesday killed top security officials.

The meeting in Doha, following a scheduled session of the organization's Syria crisis task force, will "examine the consequences of the situation in Syria from all angles," Arabi said.

Russia on Wednesday demanded the arrest and strict punishment of those behind what it called an "act of terror" in Damascus that killed three top Syrian security officials in a suicide bombing.

"We expect the organizers of the act of terror in Damascus to be identified and for them to face their deserved punishment," the Russian foreign ministry said in a statement.

The U.N. Security Council postponed a vote Wednesday on a Western-drafted resolution calling for sanctions against Syria following a request from international envoy Kofi Annan, diplomats said.

A threat by Russia, President Bashar Assad's key ally, to veto the resolution has sparked new Security Council tensions on Syria.

World powers said a suicide bombing Wednesday that killed three top Syrian officials showed the urgent need for a political transition.

"The French government, without knowing the circumstances of this attack, has always condemned terrorism. That said, given the level of violence, this makes it even more necessary and urgent to find a political transition," French Foreign Minister Laurent Fabius told the French Senate.

Iran's Revolutionary Guards on Wednesday scoffed at U.S. claims that it could Gulf waters of mines in case of conflict, after Washington announced plans for a multinational anti-mine operation.

"The Americans boast a lot about many things, but they are facing problems in practice," General Mahmoud Fahimi, deputy chief of the Guards' naval forces, told the Fars news agency.

Russia on Wednesday said a decisive battle was in progress in Syria and rejected a Western-backed U.N. resolution on the crisis as it would mean taking sides with a revolutionary movement.

"A decisive battle is in progress in Syria. Adopting the resolution would mean outright support of a revolutionary movement. And if we are talking about a revolution then the United Nations has nothing to do with it," Foreign Minister Sergei Lavrov told reporters in reference to the armed opposition to President Bashar Assad.

The rebel Free Syrian Army head has echoed fears that President Bashar Assad might resort to using chemical weapons to try to rescue his embattled regime, Al-Bayan newspaper reported on Wednesday.

"We are seeking to secure protective gas masks for civilians and (defected) soldiers ... after the regime moved some out of storage," Colonel Riad Assaad told the Dubai daily.

A suicide bomber on Wednesday struck at the heart of Syria's security apparatus, killing the country's defense minister and President Bashar Assad's brother-in-law, state television said.

The attack, which for the first time in a 16-month anti-regime uprising targeted members of Assad's inner core, came hours ahead of a U.N. Security Council debate on Syrian sanctions, when a showdown between Western powers and Russia and China is expected.