Syria has pulled its forces from on the rebel stronghold city of Homs halting days of punishing attacks just as Arab League monitors arrived in the area.
Activist group Syrian Observatory for Human Rights said at least 20,000 protesters gathered in some districts to "reveal the crimes committed by the regime."
About 60 Arab monitors - the first Syria's regime has allowed in during its nine-month crackdown on an anti-government uprising - are now in the country.
The withdrawal from Homs was the first tangible sign that President Bashar Assad was implementing the terms of the Arab League plan to halt attacks that overwhelmingly target unarmed, peaceful protesters. The monitors are supposed to ensure the government complies with the deal .
After agreeing to the plan early last week, Assad's regime only appeared to be intensifying the crackdown, rather than easing up, and it was condemned internationally for flouting the agreement.
Opposition activist Mohammed Saleh said the heavy bombardment of Homs stopped in the morning and tanks were seen pulling out.
The British-based Syrian Observatory for Human Rights said some army vehicles pulled out of Homs while other relocated in government compounds "where (they) can deploy again within five minutes."
Given the intensified crackdown, the opposition sees Syria's agreement to the Arab League plan as a farce, and some even accuse the League of complicity in the killings. Since Syria signed the deal on December 19, activists said nearly 300 civilians have been killed. About 150 more died in clashes between army defectors and troops - most of them defectors.
Syria's conflict is becoming increasingly militarised with military defectors mounting armed resistance.
The Arab League plan demands the government remove its security forces and heavy weapons from streets, start talks with opposition leaders and allow human rights workers and journalists into the country.
Opponents of Assad doubt the Arab League can budge him.
Homs, Syria's third largest city, has a population of 800,000 and is at the centre of the revolt against Assad. It is about 100 miles north of the capital, Damascus. Many Syrians refer to Homs as the "Capital of the Revolution."