BEIRUT -- Facing international condemnation for its bloody crackdown on protesters, the Syrian regime is expanding an intimidation campaign to keep people off the streets, according to human rights activists.

They report a sharp escalation in arbitrary arrests and unexplained disappearances -- including people being plucked from their homes and offices in the middle of the day. One prominent activist in an upscale Damascus neighborhood was reportedly bundled into a car after being beaten by security officers.

"Syrian cities have witnessed in the past few days an insane escalation by authorities who are arresting anyone with the potential to stage protests and demonstrations," Ammar Qurabi, who heads the National Organization for Human Rights in Syria, told The Associated Press on Tuesday.

"The arrests have transformed Syria into a large prison," he said, estimating that more than 1,000 people had been detained since Saturday in raids on houses.

Syrian forces have badly treated many detainees, Amnesty International said. One was forced to lick his own blood off the floor after he was stripped and beaten, the group said.

The stepped-up campaign will have its first major test Friday -- the main day for protests in the Arab world. But there were signs the protests will continue, with thousands of people gathering Tuesday in the coastal town of Banias, demanding freedom and urging the demise of Syria's authoritarian regime, two witnesses said.

"So far it is a peaceful protest," one person said, asking not to be identified for fear of reprisals. "Some people are carrying loaves of bread and baby's milk because our city is under siege and we can't come or go ... We are running out of supplies."

President Bashar Assad is determined to crush the six-week revolt, the gravest challenge to his family's 40-year dynasty. Assad inherited power from his father in 2000, and has maintained close ties with Iran and Islamic militant groups such as Hezbollah in neighboring Lebanon and Hamas in Gaza.

Rights groups say at least 545 Syrians have been killed since the uprising began in the blockaded southern city of Daraa, spreading quickly across the nation of some 23 million people.

Most of the unrest erupts after Muslim prayers on Fridays, and the regime's response has become increasingly brutal. Now, instead of waiting for the weekly protests, security forces are using the midweek lull to send an intimidating message.

An activist in Banias said the local branch of the political security department called a mechanic Sunday to fix one of its cars and he has not been heard from since. Three other men have been missing for days after security agents picked them up at a gas station, he said.

The activist, who asked that his name not be used for fear of government reprisal, said many people were afraid to leave their homes.

Suheir Atassi, a pro-democracy activist, asked her Twitter followers to stop calling her mobile phone because security agents have intercepted the line.

"Security (agents) are answering my mobile!" she tweeted. "They have taken over the line."

Activists' families also were affected, according to witnesses who said suspects and their relatives were being dragged from their homes in sweeping arrests. In Daraa, security forces are in cemeteries, presumably to pinpoint families of protesters who were killed.

At least two people have not been heard from since arriving at the Damascus airport: Al-Jazeera journalist Dorothy Parvaz, who landed Friday, and pro-reform writer Omar Koush, who landed Monday.

Pro-democracy activist Diana Jawabri was beaten by security agents and bundled into a car in an upscale district of Damascus, Qurabi said.

Many have been treated badly, Amnesty International said, citing interviews with detainees. The group highlighted the case of one man who said he and other men were beaten with sticks and cables, punched and kicked. The detainee said they drank dirty water from a toilet because they were given nothing to drink.

"The use of unwarranted lethal force, arbitrary detention and torture appear to be the desperate actions of a government that is intolerant of dissent," said Amnesty's Philip Luther.

The tactics recall the days of heavy-handed security rule, when even an offhand critical comment could land someone in jail for years. Under Assad's father, Hafez, who ruled with an iron fist for three decades, reports of people getting picked up on the streets and tortured were rampant.

Although most Syrians still speak of politics in hushed tones, that atmosphere became somewhat more relaxed after Bashar Assad took over in 2000. He still used state of emergency laws, in place since 1963, to crack down on dissent, arresting people without warrant or charge.

Assad did away with the emergency laws last month in response to protesters' demands, but observers say the arrests are a sign the move was not substantive.

The regime has allowed security services "to conduct business as usual, thereby illustrating just how meaningless the concept of legality was in the first place," the International Crisis Group said Tuesday.

Syria blames the unrest on a foreign conspiracy and "terrorist groups" that it says have taken advantage of protests.

State-run television flashed an urgent notice on its screen late Tuesday that said security forces arrested "a number of armed terrorist gangs" in Daraa.

Assad has acknowledged the need for reforms. He has granted citizenship to Kurds, a long-marginalized minority, to try to placate protesters, and he offered an amnesty to Syrians who turn themselves in before May 15 for carrying weapons or allegedly undermining national security.

But his overtures have been coupled with a brutal crackdown that has only emboldened protesters. In the past week, authorities intensified their campaign to quell the unrest, deploying troops and tanks to trouble spots.

State Department spokesman Mark Toner said the U.S. was very concerned about "credible reports" of the Syrian military operation in Daraa, including the use of tanks and a widespread campaign of arbitrary arrests targeting young men.

"The humanitarian situation there is quite grave," Toner said. "These are quite frankly barbaric measures. And they amount to the collective punishment of innocent civilians."

Still, Toner refused to question Assad's legitimacy as a leader. Assad needs to cease all violence against innocent protesters and address their concerns and aspirations, he said.

The Obama administration has imposed sanctions on three top Syrian officials as well as Syria's intelligence agency and Iran's Revolutionary Guard. The White House has accused Iran's hard-line regime of aiding Syria in the crackdown.

Syria is already under U.S. sanctions because it has been designated a "state sponsor of terrorism" by the State Department. The new ones extend the penalties to individuals.

European nations summoned Syrian ambassadors last week in a coordinated demand that Assad stop gunning down his people, and Germany said sanctions were possible.

"The ongoing brutal actions of the Syrian government leave the European Union no other choice than to push forward forcefully now with targeted sanctions against the regime," German Deputy Foreign Minister Werner Hoyer said Tuesday.


Associated Press writer Bradley Klapper in Washington contributed to this article.