Satellite TV channel Al Jazeera has called for the safe return of one of a journalist who has been missing in Syria since Friday afternoon.
There has been no contact with Dorothy Parvaz (39) since she disembarked from a Qatar Airways flight in Damascus on Friday.
An Al Jazeera spokesman stated: "We are deeply concerned for Dorothy's safety, security, and well-being. We are requesting full co-operation from the Syrian authorities to determine what happened at the airport, what her current location is, and the status of her health."
"We need her safe return to Al Jazeera immediately."
Syrian troops conducted door-to-door raids in cities and towns across the country today, arresting scores of people in a campaign of intimidation aimed at crushing the six-week uprising against President Bashar Assad's authoritarian regime, activists said.
Rami Abdul-Rahman, head of the Syrian Observatory for Human Rights, said hundreds of people had been arrested over the past two days alone. He said the arrests often included several members of the same family.
"The arrests are ongoing, from the besieged southern city of Daraa to the country's north and passing through the suburbs of Damascus," he said.
The arrests are part of an intensified crackdown that followed massive anti-regime protests last week.
President Assad is determined to crush the six-week-old revolt, which began in Daraa but quickly spread across the nation of some 23 million people.
Rights groups say at least 545 Syrians have been killed since authorities began their crackdown on the uprising.
Now, the once-unimaginable protests are posing the most serious challenge to four decades of rule by the Assad family in one of the most repressive and tightly controlled countries in the Middle East.
Syria-based human rights activist Mustafa Osso confirmed the massive arrests campaign, adding that the army also brought in reinforcements to the western cities of Zabadani near the Lebanese border and the northern towns of Raqqa and Idlib on Monday.
"There's heavy army presence and soldiers are conducting door-to-door raids," he said.
The Syrian military has also intensified its weeklong assault on Daraa as residents struggled to find food and bury their dead.
A drought-plagued city near the Jordanian border, Daraa has been without water, fuel or electricity for the past week, when the regime sent in troops backed by tanks and snipers to crush protests.
Syrian army tanks shelled the old quarter of Daraa yesterday and snipers nesting on rooftops and hiding in minarets have kept people cowering in fear inside their homes.
Activists said there was no news available about the town today. Many residents of the area who were in touch with the outside world through satellite phones were not picking up, while others were shut off.
"I have never been so scared in all my life," said one resident of Daraa who fled late yesterday to a nearby area some 16 kilometers away.
"Security men have divided Daraa into four parts ... there was indiscriminate shelling yesterday, people are terrified," he told AP Monday. "It's like a military barracks there."
The National Organization for Human Rights in Syria and five other rights group issued a statement Monday condemning the continuous arbitrary arrests across Syrian provinces.
Additional reporting AP