|Daraa has been the focus of protests since demonstrations began on 18 March [EPA]
Hundreds of protesters have gathered in the southern Syrian towns of Daraa and Nawa as the United Nations' human rights chief called for a probe into a weekend crackdown which left six people dead.
Daraa, the capital of Daraa governate, has been the site of unprecedented protests since Friday, with demonstrators demanding the end of the government of Bashar al-Assad, the president.
"Around 1,000 protesters gathered in and around the Omari mosque shouting anti-regime slogans, amid a heavy security and army presence," an activist in Daraa, who wished to remain anonymous, said.
The activist said the protesters in the town, a traditional home to large tribal families, had formed a human shield around the mosque on Tuesday to prevent security forces from approaching it.
An AFP photographer and videographer in Daraa, located 100km south of Damascus, the capital, said their car was stopped in the old town and they were beaten by security forces, who seized their equipment.
After being taken in for questioning, they received an apology from the authorities, but had still not found their equipment.
The photographer said soldiers were manning checkpoints at all entries to the town and were cross-checking the identity cards of all travellers with a list of names they had compiled.
Six people have been killed by security forces since the start of the demonstrations on March 18, including an 11-year-old boy who died after inhaling tear gas on Monday.
A Syrian official told the AFP news agency that the governor of Daraa had been sacked following the killings.
The official, who wished to remain anonymous, said Faisal Kalthoum was fired from his position on Tuesday.
Rula Amin, Al Jazeera's correspondent in Damascus, said that Kalthoum had not officially been sacked but had not been seen in public for the past three days.
Navi Pillay, the UN High Commissioner for Human Rights, has called on Syrian authorities to carry out a transparent probe into the weekend crackdown and to halt the excessive use of force.
"The government should carry out an independent, transparent and effective investigation into the killings of the six protesters during the events of 18 and 20 March," Rupert Colville, a spokesman for Pillay, said on Tuesday.
"We are greatly concerned by the recent killings of protesters in Syria and reiterate the need to put an immediate halt to the excessive use of force against peaceful protesters, especially the use of live ammunition."
Colville said that the use of excessive force was a "clear violation of international law" and that perpetrators could be prosecuted.
"People have the legitimate right to express their grievances and demands to their government, and we urge the Syrian government to enter into a broad, meaningful dialogue with the protesters in an attempt to address those grievances," he said.