Syria's government showed off TV and still images of burned buildings and rubble-strewn streets empty of people in Hama, the epicenter of anti-regime protests, and claimed Friday it was putting an end to the rebellion in the besieged city.

Under the suffocating clampdown, residents of the city warned that medical supplies were running out and food was rotting after six days without electricity.

Across the country, tens of thousands of protesters marched, chanting their solidarity with Hama and demanding the ouster of President Bashar Assad. They were met by security forces who opened fire, killing at least 13 people, activists said.

Also on Friday, the U.S. State Department urged Americans to leave the country immediately

Government forces began their ferocious assault on Hama Sunday, cutting off electricity, phone services and Internet and blocking supplies into the city of 800,000 as they shelled neighborhoods and sent in tanks and ground raids.

It appeared to be an all-out attempt to take back the city _ which has a history of dissent _ after residents all but took it over since June, barricading it against the regime. Rights group say at least 100 people have been killed, while some estimates put the number as high as 250.

The tolls could not be verified because of the difficulty reaching residents and hospital officials in the city, where journalists are barred as they are throughout Syria.

Tanks shelled residential districts of Hama starting around 4 a.m. Friday, just as people were beginning their daily fast for the Muslim holy month of Ramadan _ mirroring a bombardment the evening before at sunset, when people were breaking the fast, one resident told The Associated Press.

"If people get wounded, it is almost impossible to take them to hospital," the resident said by telephone, speaking on condition of anonymity for fear of retaliation.

Syrian state media on Friday proclaimed army units were "working to restore security, stability and normal life to Hama," which it said had been taken over by "terrorists." The message mirrored the regime's claim that armed extremists seeking to destabilize the country are behind the unrest, as opposed to true reform-seekers.

For the first time since the siege began, government-run TV and the state news agency aired images of the ravaged streets of Hama, strewn with debris, damaged vehicles and makeshift barricades. In one, a yellow taxi was shown with a dead man in the driver's seat and bloodstains on the door. A tank cleared away a large cement barrier and a bus with shattered windows.

There were no reports of protests in the city during the day Friday _ a contrast to previous weeks when hundreds of thousands participated in the biggest marches in the country.

A citizen journalist from Hama working with an online global activist group, Avaaz, told AP that people were now too afraid to go to the mosques, which were being targeted by the military.

The man, who identified himself as Sami, described the humanitarian situation as "catastrophic." Everything was closed, including bakeries and pharmacies, he said.

"There are sick people, people with diabetes who have run out of insulin ... The food has spoiled because there's no electricity," he said. "You cannot imagine how tired and terrified people are."

Hama has seen government crackdowns before. In 1982, Assad's father, Hafez Assad, ordered the military to quell a rebellion by Syrian members of the conservative Muslim Brotherhood movement there, sealing off the city in an assault that killed between 10,000 and 25,000 people.

Witnesses have painted a grim picture of life in Hama. One resident said Thursday that people were "being slaughtered like sheep while walking in the street." He spoke on condition of anonymity for fear of reprisals.

There were also fears of an intensified assault on the oil center of Deir el-Zour to the east, where tanks have been deployed at entrances since earlier this week. Rami Abdul-Rahman, head of the London-based Observatory for Human Rights in Syria, said a quarter of the city's population of 600,000 have fled.

Friday has become the main day for protests in Syria, despite the near-certainty that tanks and snipers will respond with deadly force.

Still, the latest protests were smaller than those of previous Fridays, when hundreds of thousands turned out nationwide. That was likely because this was the first Friday of Ramadan, when Muslims fast from dawn to dusk and go outside less, particularly in the summer heat.

The lower turnout could augur disappointment for protest leaders, who had hoped to escalate the uprising and even mark a turning point in the quest to topple the 40-year Assad family dynasty's rule.

Protests on Friday spread from the capital, Damascus, to the southern province of Daraa, the central city of Homs and in Qamishli, near the Turkish border. Some 20,000 people protested in Deir el-Zour, lower than the hundreds of thousands of previous weeks, likely due to the flight of a large part of the population.

"Hama, we are with you until death," shouted a crowd marching through Damascus' central neighborhood of Midan, clapping their hands and chanting, "We don't want you Bashar!" in amateur video posted online by activists.

In another district of the capital, Qadam, protesters carried a banner reading, "Bashar is slaughtering the people and the international community is silent."

Security forces opened fire with live ammunition and tear gas in several cities, activists said. At least 10 people were killed in the Damascus suburbs of Arbeen, Moaddamiya and Dumeir, and three others in Homs, according to the Observatory for Human Rights and the Local Coordination Committees, a group that tracks protests.

One man who had been arrested earlier was found dead outside his home in the Damascus neighborhood of Qaboun with torture marks on his body, the Observatory said.

Activists also said about 50 people were wounded in Friday's protests.

State-run TV reported that two policemen were killed and eight wounded when they were ambushed in the northern town of Maarat al-Numan.

The uprising, now in its fifth month, has proved remarkably resilient, continuing daily and expanding despite a bloody crackdown that has killed at least 1,700 people.

But protesters have so far failed to mobilize the middle class and Muslim Sunni elite to form a real threat to Assad's minority Alawite rule. Organizers had hoped to garner the increased religious fervor of Ramadan to give the protests a further boost. But so far that has yet to materialize.

Since the start of Ramadan on Monday, many anti-government protesters were choosing instead to stage nightly protests, usually numbering in the thousands, following special Ramadan nighttime prayers.

The U.S. State Department urged Americans to leave the country immediately and advised those who remain in the country to restrict their movements. The warning came as congressional calls grew for the Obama administration to impose severe new sanctions on President Bashar Assad's regime.

In a new travel warning, the department said Americans should depart Syria while commercial flights and other transportation are still available "given the ongoing uncertainty and volatility of the situation." It noted that Syrian authorities had imposed tight restrictions on the ability of U.S. and other diplomats to move around the country.

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Zeina Karam and Bassem Mroue can be reached at http://twitter.com/zkaram and http://twitter.com/bmroue