Russia on Friday dismissed as "rumors" speculation on the Internet that the wife of President Bashar Assad had taken refuge in the country amid the escalating violence in Syria.

Asma Assad has not been seen recently in public in Syria, giving rise to speculation, which started on the micro-blogging service Twitter, that she may have sought refuge in Syria's remaining ally Russia.

Russia will delay its controversial shipment of three attack helicopters and an air defense system to Syria until security is restored in the country, the Interfax news agency reported on Friday.

"The decision to delay the Syrian delivery timeframe is based on the escalating military and political situation in the country and the act of terror in which several senior Syrian officials were killed and injured," the unnamed military source told the news agency.

Russia has detained four men suspected of organizing an assassination attempt on the Islamic leader of Russia's main Muslim region and killing another top cleric, investigators said Friday.

Moscow-based investigators said the main reason for the double attacks in the oil-rich republic of Tatarstan -- often praised for its religious tolerance -- was the clerics' fight against Muslim radicals.

Comments by Russia's envoy to Paris that Syrian President Bashar al-Assad is ready to give up power in a "civilized manner" are "totally baseless," Syrian state television said on Friday.

"The comments attributed to the Russian ambassador to Paris on the fact that President Assad would agree to relinquish power in a civilized manner are totally baseless," the broadcaster said.

Russia on Friday slammed the "unacceptable" Western criticism that followed its decision to block together with China the threat of sanctions against its ally Syria at the U.N. Security Council.

"It is absolutely unacceptable that some Western countries are trying to lay the blame for the escalating Syrian violence on Russia's refusal to support a resolution threatening sanctions against the authorities," foreign ministry spokesman Alexander Lukashevich told reporters.

Russia and China on Thursday vetoed a U.N. Security Council resolution that would threaten sanctions against Syria's President Bashar Assad if he does not end the use of heavy weapons.

The third Russia-China veto in nine months opened up an acrimonious battle at the 15-nation council over who is to blame for the world powers' failure to get international action to halt the Syria conflict.

The Islamic leader of Russia's main Muslim region of Tatarstan was wounded Thursday and another cleric killed in rare attacks in an oil-rich republic often praised for its religious tolerance.

The Mufti of Tatarstan, Ildus Faizov, was wounded in a car explosion while his former deputy, Valiulla Yakupov, was shot dead in the strikes an hour apart as Muslims prepared to begin observing Ramadan at sundown.

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.

A Russian ship that tried to supply attack helicopters to Syria last month before being forced back will dock in Saint Petersburg in coming days, its owners said on Wednesday.

The privately-chartered Alaed had to return to Russia after its initial attempt to deliver the controversial cargo to President Bashar Assad's regime in June was exposed by the U.S. State Department.

Russian President Vladimir Putin told visiting Syria peace mediator Kofi Annan on Tuesday that he would "do everything" to support the U.N.-Arab League envoy's plan to end the conflict.

"From the very start, from the first steps, we supported and continue to support your efforts aimed at restoring civil peace," Putin told Annan at the start of their Kremlin meeting.