Elite Syrian forces moved swiftly through the country's restive north on Friday, raining tank shells on rebellious towns, torching farmland and shooting protesters who tried to tear down a poster of President Bashar Assad, activists and refugees said.

At least 32 people were killed, activists said, and undaunted protests extended to every major city.

The leader of neighboring Turkey, angered by violence that has sent more than 4,000 Syrians streaming across the border, accused the Assad regime of "savagery."

Backed by helicopters and tanks, the troops responsible for most of Friday's violence were believed to be from an elite division commanded by Assad's younger brother, Maher. The decision to mobilize his unit against the most serious threats to the 40-year Assad regime could be a sign of concern about the loyalty of regular conscripts.

Syrians who escaped from the town of Jisr al-Shughour into Turkey said the army came after police turned their guns on each other and soldiers refused orders to fire on protesters last week. Syrian state television has said 120 officers and security personnel were killed by gunmen. A man who remained behind said the few residents left were hoping barricades of burning tires could hold off the reinforcements surrounding them.

Twenty-five miles (40 kilometers) to the southeast in the town of Maaret al-Numan, thousands of protesters overwhelmed security officers and torched the courthouse and police station, and the army responded with tank shells, a Syrian opposition figure told The Associated Press by telephone, speaking on condition of anonymity because of the sensitivity of the matter.

Syria's state-run television appeared to confirm at least part of the report, saying gunmen opened fire on police stations, causing casualties among security officials.

Syria's government has a history of violent retaliation against dissent, including a three-week bombing campaign against the city of Hama that crushed an uprising there in 1982. Jisr al-Shughour itself came under government shelling in 1980, with a reported 70 people killed.

Confirming information out of Syria is difficult. Communications are cut in areas where the uprising is strongest. Syrians who speak openly face retribution from the regime, and foreign journalists have been expelled.

Refugees trying to escape into Turkey, who now number more than 4,000, gave a more detailed picture of the events in the north.

A group of young men who arrived at the Turkish village of Guvecci on Friday said relatives who stayed behind told them Syrian forces were burning homes and fields in the village of Sirmaniyeh, near Jisr al-Shughour. One of the men said a helicopters had fired on a mosque there, the refused to say anything more.

"They are burning down everything there," said a young man who gave his name as Adil. "They said they even killed animals. The people have no weapons, they can't defend themselves. The only thing they can do is escape."

As he spoke another Syrian got a call telling him his cousin had died in Latakia, where activists said security forces fired on protesters who tried to tear down a giant poster of Assad, killing seven. The young man whose phone rang slumped and wept.

The Local Coordination Committees, a group that documents anti-government protests in Syria, said 32 people were killed on Friday, half of them in Idlib, the province home to Maaret al-Numan and Jisr al-Shughour. Late Friday, Syrian television said troops reached the entrances of Jisr al-Shughour and detained members of "armed groups."

Citing contacts inside Syria, Rami Abdul-Rahman, the London-based head of the Syrian Observatory for Human Rights, said more than 10,000 soldiers were involved.

Witnesses contacted by telephone said most residents had abandoned the town of up to 45,000.

Syria's government invited an AP reporter to accompany troops to Jisr al-Shughour, apparently reflecting a new effort to counter criticism and prove the existence of armed gangs.

In Sirmaniyeh, where the refugee reported the torching of homes and fields, journalists accompanying Syrian troops in the morning saw a parked army bus, its front windshield smashed by gunfire. The army said the bus was ambushed early Friday, and that driver escaped unhurt after a bullet struck his protective vest.

Journalists were also shown eight grenades on a roadside in Ziara, another village in the area.

"Now we feel safe," said Walida Sheikho, a 50-year-old woman who welcomed the troops in the village of Foro, near Jisr al-Shughour.

She and other residents offered food, water and juice to the Syrian troops and said they had appealed for help from the army.

Jisr al-Shughour is a predominantly Sunni town with some Alawite and Christian villages nearby. Most Syrians are Sunni Muslim, but Assad and the ruling elite belong to the minority Alawite sect, an offshoot of Shiite Islam.

State television said armed groups torched crops and wheat fields around Jisr al-Shughour as the army approached.

A man in the town blamed security forces for the crop-burning. He said the few remaining residents were collecting tires to burn in an attempt to try to block the army advance. Speaking by phone, he told an AP reporter in Beirut that about 40 tanks rolled into a village five miles (12 kilometers) from Jisr al-Shughour. He and other activists reported hearing bursts of machine gun fire.

Other protests in Syria occurred in neighborhoods in the capital, Damascus, and the major city of Aleppo, which are vital to Assad's authoritarian regime. But the demonstrations in those cities have been relatively limited in scope compared to other restive areas.

Activists said security forces opened fire on protesters near the Sheikh Jaber mosque in the Damascus suburb of Qaboun, killing three people and wounding several others. One activist, who spoke on condition of anonymity for fear of reprisals, said there were snipers on rooftops and security checkpoints outside local mosques.

Turkish Prime Minister Recep Tayyip Erdogan has said he will keep the frontier open to Syrians fleeing violence, and the Turkish military was increasing border security to better manage the refugee influx. He singled out Assad's brother for criticism.

"I say this clearly and openly, from a humanitarian point of view, his brother is not behaving in a humane manner. And he is chasing after savagery," Erdogan said late Thursday.

Human rights groups say the crackdown has killed more than 1,400 people, most of them unarmed civilians. The government says a total of 500 security forces have also been killed.

"Unfortunately, it is clear that things are not going in the right direction," Turkish President Abdullah Gul said, according to the Anatolia news agency. "We are following things with sadness."

On Friday, U.N. Secretary General Ban Ki-moon issued a note highlighting his deep concern over the continuing violence in Syria and its heavy toll on the civilian population and called on the government to respect the rights of the Syrian people.

U.N. spokesman Martin Nesirsky said that Ban tried to speak with Assad several times, but he would not come to the phone.

"The Secretary General has been keen to speak to Assad. He tried to place a call yesterday but unfortunately the president was not available," Nesirsky said. "He tried to place the call more than one time but he was not available."

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Karam reported from Beirut. Associated Press writer Albert Aji in the Jisr al-Shughour area contributed to this report.