Syrian tanks firing shells and machineguns stormed the city of Hama, killing at least 45 civilians in a move to crush demonstrations against president Bashar al-Assad's rule, residents and activists said.
Mr Assad's forces began their assault on the city, scene of a 1982 massacre, at dawn after besieging it for nearly a month. The official state news agency said scores of were on rooftops and "shooting intensively to terrorize citizens".
But residents said tanks and snipers were shooting at unarmed residential districts, where inhabitants had set up makeshift road blocks to try and stop their advance, and that an irregular Alawite militia loyal to Assad, known as 'shabbiha'accompanied the invading forces in buses.
Hama has particular significance for the anti-Assad movement as Mr Assad's father, the late president Hafez al-Assad, sent in troops to crush an Islamist-led uprising there in 1982, razing whole neighbourhoods and killing up to 30,000 people in the bloodiest episode of Syria's modern history.
The president and the ruling family are from the minority Alawite sect, which has dominated Syria, a majority Sunni country, since the ruling Baath Party took power in a 1963 coup.
In 2000, Mr Assad succeeded his late father, keeping the autocratic political system he inherited intact, while expanding the share of the Assad family of the economy through monopolies awarded to relatives and friends.
Citing hospital officials, the Syrian Observatory for Human Rights said the death toll in Hama was likely to rise, with dozens badly wounded in the attack.
A doctor, who did not want to be further identified for fear of arrest, said that most bodies were taken to the city's Badr, al-Horani and Hikmeh hospitals.
Scores of people were wounded and blood for transfusions was in short supply, he said by telephone from the city, which has a population of around 700,000.
"Tanks are attacking from four directions. They are firing their heavy machineguns randomly and overrunning makeshift road blocks erected by the inhabitants," the doctor said, the sound of machinegun fire crackling in the background.
The state news agency said military units were fighting gunmen armed with rocket propelled grenades and machineguns.
"Armed groups in Hama set police stations on fire, vandalised public and private property, set roadblocks and barricades and burned tyres at the entrance of the city and in its streets."
Tank shells were falling at the rate of four a minute in and around northern Hama, residents said, and electricity and water supplies to the main neighbourhoods had been cut, a tactic used regularly by the military when storming towns to crush protests.
Mr Assad is trying to end an uprising against his 11-year rule that broke out in March, inspired by the Arab Spring revolutions in Tunisia and Egypt, and has spread across the country.
Syrian authorities have expelled most independent journalists, making it difficult to verify reports of violence.
In southern Syria, rights campaigners said security forces killed three civilians when they stormed houses in the town of al-Hirak, 35 km northeast of the city of Deraa.
Local activists and the Syrian Observatory for Human Rights added dozens of people, including three women, were arrested.
The Observatory said troops also arrested more than 100 people in the Damascus suburb of Mouadamiyah. A Western diplomat said he saw several tanks enter the suburb.
"The regime thinks it can scare people before Ramadan and make them stay home. But especially the people of Hama have shown themselves to be resilient," the diplomat said.
The US ambassador to Syria, Robert Ford, visited Hama earlier this month in a gesture of international support for what he described as peaceful pro-democracy demonstrations.
The Syrian leadership blames "armed terrorist groups" for most of the killings during the revolt, saying that more than 500 soldiers and security personnel have been killed.
An activist group, Avaaz, said in a report last week that Syrian security forces had killed 1,634 people in the course of their crackdown, while at least 2,918 had disappeared. A further 26,000 had been arrested, many of whom were beaten and tortured, and 12,617 remained in detention, it said.
In the east of the country, Syrian forces began an assault two days ago in a tribal oil-producing province on the border with Iraq's Sunni heartland. Residents said at least 11 civilians were killed in the eastern provincial capital of Deir al-Zor yesterday and today.
The Syrian Revolution Coordination Union, said 57 soldiers in Deir al-Zor, including two lieutenants and a captain, had defected to the demonstrators. It said residents had formed local committees and erected makeshift barriers to try to halt the advance of tanks and armoured vehicles inside the city.
"More tank columns are heading to Deir al-Zor. By using heavy weapons, security forces are waging war against their own people," the group said in a statement.
The official state news agency said: "Armed groups in Deir al-Zor cut off roads, terrorised citizens and attacked police."
It added: "An exchange of fire occurred. The police forces confronted these armed groups and are still chasing them ... The inhabitants of Deir al-Zor have expressed their rejection of these actions which are bad for the homeland."
Reuters