Despite the arrival of Arab peace monitors, 15 people are said to have been killed in Syria – the latest victims in a weekend of more bloodshed.
In the flashpoint city of Homs, some 70,000 protesters, emboldened by the presence of the observers, confronted security forces.
Unverified video posted on the internet appeared to show activists urging the observers to venture into areas where clashes have been especially fierce, calling for international protection.
The 50-strong Arab delegation is in Syria to determine if President Bashar al-Assad is keeping his promise to implement a peace plan.
Although never allowed to wander away from government minders, the leader of the mission claimed the first visit had gone well.
But activists said the tanks only left as the monitors arrived and later, when they withdrew, more violent clashes broke out.
The UN says at least 5,000 lives have been lost in Syria since the protest movement began nine months ago.
To counter claims of a popular peaceful revolt, Syrian state-run television reported that stacks of weapons had been seized from what were described as Islamist terrorists.