Thousands of soldiers backed by tanks and snipers moved in before dawn to the city where Syria's anti-government uprising began, causing panic in the streets when they opened fire indiscriminately on civilians and went house-to-house rounding up suspected protesters. At least 11 people were killed and 14 others lay in the streets -- either dead or gravely wounded, witnesses said.

The military raids on the southern city of Daraa and at least two other areas suggested Syria is trying to impose military control on the centers of protests against President Bashar Assad, whose family has ruled Syria for four decades. Residents and human rights activists said the regime wants to terrify opponents and intimidate them from staging any more demonstrations.

The offensive was meticulously planned: Electricity, water and mobile phone services were cut. Security agents armed with guns and knives conducted house-to-house sweeps, neighborhoods were sectioned off and checkpoints were erected before the sun rose.

"They have snipers firing on everybody who is moving," a witness told The Associated Press by telephone. "They aren't discriminating. There are snipers on the mosque. They are firing at everybody," he added, asking that his name not be used for fear of retribution.

The massive assault on Daraa appeared to be part of new strategy of crippling, pre-emptive strikes against any opposition to Assad, rather than reacting to demonstrations. Other crackdowns and arrest sweeps were reported on the outskirts of Damascus and the coastal town of Jableh -- bringing more international condemnation and threats of targeted sanctions by Washington.

Razan Zeitounia, a human rights activist in Damascus, said the widespread arrests -- including of men along with their families -- appear to be an attempt to scare protesters and set an example for the rest of the country.

As the Syrian government stepped up its crackdown, the U.S. State Department urged Americans to defer all travel to Syria and advised those already in the country to leave while commerical transportation is still available. It also ordered some nonessential U.S. embassy staff and the families of all embassy personnel to leave Syria. It said the embassy would remain open for limited services.

The attack on Daraa, an impoverished city on the Jordanian border, was by far the biggest in scope and firepower. Video purportedly shot by activists showed tanks rolling through streets and grassy fields with soldiers on foot jogging behind them.

Witnesses said busloads of troops poured in before dawn and snipers took up positions on the roofs of houses and high buildings while other security agents searched houses for suspected protesters.

"They are entering houses. They are searching the houses," said one witness. "They are carrying knives and guns."

He said people were crying out over mosque loudspeakers for doctors to help the wounded and there was panic in the streets.

"We need international intervention. We need countries to help us," shouted another witness in Daraa, who said he saw five corpses after security forces opened fire on a car. He spoke to the AP by telephone.

The forces occupied two mosques and a graveyard.

"Let Obama come and take Syria. Let Israel come and take Syria. Let the Jews come," shouted one Daraa resident over the phone. "Anything is better than Bashar Assad," he said, playing on Syria's hatred for Israel to highlight how much town residents despise their leader.

All witnesses spoke on condition of anonymity for fear of reprisals.

Daraa, a drought-parched region of 300,000 in the south, has seen some of the worst bloodshed over the past five weeks as the uprising gained momentum. The area was ripe for unrest: The grip of Syria's security forces is weaker on the border areas than around the capital, Damascus, and Daraa hasn't benefited from recent years of economic growth. Meanwhile, Daraa has absorbed many rural migrants who can no longer farm after years of drought.

The city of Daraa was where Syria's uprising began in mid-March, touched off by the arrest of teenagers who scrawled anti-government graffiti on a wall.

A relentless crackdown since mid-March has killed more than 350 people throughout the country, with 120 alone dying over the weekend. But that has only emboldened protesters, who started with calls for modest reforms but are now increasingly demanding Assad's downfall.

State-run television quoted a military source as saying army units entered the city to bring security "answering the pleas for help by residents of Daraa."

Another military raid targeted the Damascus suburb of Douma, where rattling, heavy gunfire could still be heard late Monday. Soldiers, masked men in black uniforms and plainclothes security forces were manning checkpoints made from mounds of dirt throughout the area, a resident said.

In Jableh, men who tried to leave their houses were shot at by soldiers and thugs, three residents said, and only women were allowed onto the streets to buy food. Some quietly managed to bury seven men and a woman who were killed by security forces the day before, witnesses said. Security forces banned them from conducting funeral marches that frequently morph into protests.

Syria has banned nearly all foreign media and restricted access to trouble spots since the uprising began, making it almost impossible to verify the dramatic events shaking one of the most authoritarian, anti-Western regimes in the Arab world.

Syria is a close ally of Iran and a backer of the militant groups Hezbollah in Lebanon and Hamas in Gaza.

There were conflicting reports about whether authorities sealed the Syrian border with Jordan, although the head of Syria's Customs Department said crossings at the frontier were open as normal.

A Jordanian taxi driver said the border was open, but the main highway linking Syria with Jordan was blocked.

"The situation on the highway is scary," he said. "Protesters are burning tires and hurling stones at the army, which is responding with live fire, shooting randomly at civilians."

Assad has blamed most of the unrest on a "foreign conspiracy" and armed thugs, and has used state media to push his accusations.

The violence has exacerbated sectarian tensions that had largely been kept in check under Assad's iron rule and secular ideology. The majority of the population is Sunni Muslim, but Assad and the ruling elite belong to the minority Alawite sect, an offshoot of Islam's Shiite branch that dominates in Iran, Iraq and Bahrain.

On Monday, Syrian TV repeatedly ran lingering, gruesome close-ups of dead soldiers, their eyes blown out and parts of their limbs missing, to back up their claims that they were under attack. The channel then turned to showing soldiers' funeral marches, with men waving red, black and white Syrian flags and hoisting photos of Assad.

Unrest in Syria has repercussions well beyond its borders.

Syria has a pivotal role in most of the flashpoint issues of the Middle East -- from the Arab-Israeli peace process to Iran's widening influence. Instability has thrown into disarray the U.S. push for engagement with Damascus, part of Washington's hopes to peel the country away from Hamas, Hezbollah and Tehran.

The White House said Monday it was considering sanctions against the Syrian government in response to the brutal crackdown. The statement from National Security Council spokesman Tommy Vietor was the first time officials had said publicly that sanctions were possible.

Syria already is subject to numerous penalties as it is deemed a "state sponsor of terrorism" by the State Department, but it maintains diplomatic relations with Washington.

In recent days, there had been signs that the regime was planning to launch a massive push against the opposition.

Last week, Assad fulfilled a key demand of the protest movement by abolishing nearly 50-year-old emergency laws that had given the regime a free hand to arrest people without cause. But he coupled the concession with a stern warning that protesters would no longer have an excuse to hold mass protests, and any further unrest would be considered "sabotage."

When protesters defied his order and held demonstrations Friday -- the main day for protests around the Arab world -- they were met with a gunfire, tear gas and stun guns.

At the United Nations, France, Britain, Germany and Portugal were urging the U.N. Security Council to strongly condemn the violence against peaceful demonstrators. The four European nations circulated a draft media statement to other council members that will be discussed at a meeting on Tuesday afternoon.

The United States is supporting the statement of condemnation, a Security Council diplomat said, speaking on condition of anonymity because he was not authorized to speak publicly. But whether the Security Council makes any statement is likely to depend on Russia and China, both veto-wielding council members with close ties to Syria.

In Geneva, the U.N. human rights chief, Navi Pillay, said Syria has turned its back on international calls to "stop killing its own people."