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Syrian security forces went door-to-door in cities throughout the country today, detaining hundreds of people in an attempt to thwart antigovernment protests that began in mid-March. The tactic appears to be borrowed from Iran, which shut down a massive antiregime protest movement of its own two years ago and is reportedly taking an increasing role in helping Syria's Assad regime contain the revolt.

Today's Syrian raids targeted the coastal city of Banias, the city of Homs in eastern Syria, some of the Damascus suburbs, and towns around the southern city of Deraa, where the protests first erupted in March, the Associated Press reports.

At this point, the death toll is estimated to have topped 800, according to human rights groups in contact with people in the country, and tanks and troops are deployed in several cities, imposing curfews and communication blackouts. Large numbers of military troops and tanks moved into Homs, Banias and Tafas, outside Deraa, on Sunday.

Reports vary about the number of newly dead in those cities, Homs in particular. All reports cite gunfire and casualties.

The widespread arrests and climbing death toll have sent activists into hiding at a time when the leaderless uprising was expected to begin coalescing behind figureheads, according to the Associated Press. Turnout for Friday's protests across the country was 30 percent lower than for the previous week's protests, at least partially because of security forces' use of detention and intimidation. Estimates of the number of detained run as high as 10,000.

According to a statement from SANA News Agency, which carries government statements, more than 900 people have "turned themselves in" for their involvement in "riot acts." The statement said that there will be no punishment for those who hand themselves over prior to May 15.

However, an opposition figure told the Guardian that hostility to President Bashar al-Assad's rule has grown so much that it will be impossible to crush. When the protests first began, protesters were demanding an end to emergency rule and other forms of repression, but not the end of Assad's rule. Now, his removal is a common demand.

"The shocks of the military campaign are being absorbed," he said. "We have seen that as soon as the Army withdraws or lessens its presence in one area to crush people elsewhere, protests erupt in the area the forces had left."

The government continues to blame the unrest and deaths – including those of 10 civilians who were killed Sunday in an ambush on a bus returning from Lebanon – on "armed terrorists."

However, Al Jazeera reported that observers in Homs, which is near where the ambush took place, doubted the government's account. The Army and security force presence is particularly heavy in that area, they said, and "scores" of protests had been killed over the weekend.

Western diplomats based in Damascus say that Iran's role in the government crackdown is growing, the Guardian reports. They say that the number of Iranian personnel in the country is growing and that the door-to-door detentions is a tactic borrowed from Iran's brutal crackdown on the June 2009 protests that followed the country's presidential election. The White House made similar assertions of Iranian involvement last month.

Iranian news outlets have blamed the violence on foreign violence and terrorists.

“We have to understand the reason behind this kind of development…. We have to understand there are weapons, traitors, and terrorists,” Syrian lawmaker Muhammad Habash was quoted as telling Iran's Press TV. “My message … to our people [is that] we have to respect our Army and we have to respect the security in Syria.”

Hundreds of Syrians staged a sit-in near the US embassy in Damascus to protest what they considered US interference in Syria's internal affairs, SANA reports. The US sanctioned several Syrian government officials last week and has harshly criticized the Assad regime's crackdown on protesters.