A looming ceasefire deadline has not stopped Syrian forces loyal to President Bashar al-Assad from shelling two cities in a bid to weaken opposition forces.
Tank and sniper fire continued to pound the central city and protest nexus of Homs, and the town Zabadani near Damascus.
Rebel fighters also kept up their attacks, reportedly killing three soldiers in separate actions in Aleppo and Idlib.
Assad has formally agreed to a ceasefire negotiated by UN-Arab League envoy Kofi Annan from April 10th.
But Syrian opposition figures as well as Western governments have already said they are not convinced Assad, who has failed to honor previous commitments, will abide by the ceasefire.
The opposition Syrian National Council has endorsed Annan's six-point peace plan, but made no official comment on the April 10th ceasefire target.
Rebels of the Free Syrian Army have said they will stop their if tanks and artillery withdraw from cities as agreed.
Syria's ambassador to the United Nations, Bashar Ja'afari, said Damascus would not take all the blame if the plan failed. He added that Annan must also get the armed opposition to comply.
"A plan wouldn't be successful unless everybody is committed to it," Ja'afari said in New York.
Annan's office said Tuesday that an advance team from the United Nations' peacekeeping department will arrive in Damascus within two days to work out how observers can monitor the truce.
A team of up to 250 unarmed observers is envisaged although it will require a Security Council resolution.
Many foreign governments fear the conflict could descend into a full-scale civil war and drag in other Middle East players if it carries on much longer.
UN Human Rights officials estimate Assad's forces have killed more than 9,100 people in the year-long popular uprising against his autocratic rule.
Damascus claims about 3,000 security personnel have been killed by what it describes as "foreign-backed gangs of terrorists."