A senior Syrian military defector has said President Bashar al Assad's forces are set to use chemical weapons to "perpetrate a sea of blood".
General Mustafa Sheikh, who fled the army in January, said regime forces wanted to "burn the country".
"The regime has started moving its chemical stockpile and redistributing it to prepare for its use," he said in an interview with the Reuters news agency.
"They are moving it from warehouses to new locations. They want to burn the country. The regime cannot fall without perpetrating a sea of blood."
Syria has denied any plans to use chemical weapons.
The country's 16-month conflict has been transformed since Wednesday, when a bomb killed four members of Mr Assad's narrow circle of lieutenants.
Those killed included his powerful brother-in-law, defence minister and intelligence chief.
Western and Israeli officials, concerned that chemical stockpiles could fall into the hands of militants, said a week ago that Syria appeared to be shifting weapons from storage sites.
However it was not clear whether the operation was a security precaution or a preparation for deployment.
General Sheikh said the coming days would see increased shelling of Sunni Muslim strongholds in Damascus and Aleppo.
"The coming phase will witness a phase of bloodshed that is unprecedented and the regime will resort to non-conventional weapons. Every action will trigger a bigger reaction."
Meanwhile, United Nations Security Council has voted unanimously to extend its monitoring mission in Syria - after some of the worst violence of the uprising.
More than 50 people were killed in Damascus on Friday as rebels intensified their guerrilla fight to topple Mr Assad's regime.
It was the sixth consecutive day of fighting in districts across the capital.
The rebels ambushed troops and attacked police stations as thousands of civilians fled to Lebanon and Iraq to escape the conflict.
The 30-day mission is considered crucial to implementing international envoy Kofi Annan's six-point peace plan, which has been flouted by President Bashar al Assad's government.
Some 300 unarmed observers suspended their mission last month because of escalating violence.
Three Syrian generals have crossed into Turkey in recent days, bringing the number of generals who have fled the unrest in Syria to 24.