Prime Minister Stephen Harper has blasted the Syrian regime's violent crackdown against demonstrators on Sunday in the lead-up to the Muslim holy month of Ramadan, calling the raids against civilians "abhorrent."

"Canada strongly condemns the latest violent and abhorrent assault by Syrian security forces against peaceful protesters, in particular the brutal attack on Hama," the statement said, adding that the use of military force and tanks to suppress people was "utterly indefensible."

The Syrian army raided cities across the country before dawn Sunday, killing up to 140 people — most of them in the flashpoint city of Hama where a barrage of shelling and gunfire left bodies scattered in the streets, activists and residents said.

The government is escalating its crackdown on protests calling for President Bashar Assad's ouster ahead of Ramadan, which starts Monday. Demonstrations are expected to swell during Ramadan in a remarkably resilient uprising that began in mid-March.

Harper's statement urged the Syrian government to either deliver the reforms that the Syrian people were demanding, or relinquish power so those reforms can be achieved.

Harper to Assad: 'Get out of the way'

"The Syrian President is faced with a clear choice: Deliver the reform that the Syrian people are asking or get out of the way so others can deliver it," the statement said.

Estimates of the death toll from the recent attacks were impossible to verify, ranging from 120 to 140. The attacks began before dawn and witnesses said they were too frightened to collect bodies from the streets. Human rights group Sawasiah said at least 80 of those deaths were in Hama.

U.S. President Barack Obama called the reports "horrifying" and said Assad is "completely incapable and unwilling" to respond to the legitimate grievances of the Syrian people.

Germany has requested that the UN Security Council meet Monday to discuss the worsening violence.

Having sealed off the main roads into Hama almost a month ago, army troops in tanks pushed into the city before daybreak Sunday in a co-ordinated assault. Residents shouted, "God is great!" and threw firebombs, stones and sticks at the tanks. The crackle of gunfire and thud of tank shells echoed across the city, and clouds of black smoke drifted over rooftops.

"It's a massacre. They want to break Hama before the month of Ramadan," an eyewitness who identified himself by his first name, Ahmed, told The Associated Press by telephone from the city.

Hospitals were overwhelmed with casualties and were seeking blood donations, he said.

While the military onslaught against Hama residents seems massive, L.A. Times reporter Borzou Daragahi told CBC News on Sunday that the city remains in control of the opposition. Daragahi was en route to the city and bases his report on activist accounts and video footage.

Soldiers in tanks fire machine-guns, others defect

During Ramadan, Muslims throng mosques for special night prayers after breaking their daily dawn-to-dusk fast. The gatherings could trigger intense protests throughout the predominantly Sunni country and activists say authorities are moving to ensure that does not happen.

Other raids were reported in southern Syria and in the suburbs of the capital Damascus. In the neighbourhood of al-Joura in the eastern city of Deir el-Zour, soldiers in tanks fired machine-guns, killing at least seven people, activists said.

In the village of al-Hirak in the southern province of Daraa, residents said security forces killed four people early Sunday after opening fire on residents as people ventured into the streets to buy bread.

A resident who gave his name as Abu Mohammed said more than 40 were wounded and 170 detained in house-to-house arrests.

He said some soldiers defected to the protesters after having refused orders to shoot at civilians.

British foreign secretary calls raids 'shocking'

The reports could not be independently verified because Syria has banned most foreign media and restricted coverage.

British Foreign Secretary William Hague said the attacks against civilians were "all the more shocking" on the eve of Ramadan and appeared to be part of a "co-ordinated effort to deter Syrians" from protesting in advance of the Muslim holy month.

"President Bashar is mistaken if he believes that oppression and military force will end the crisis in his country. He should stop this assault on his own people now," Hague said in London.

An estimated 1,600 civilians have died in the crackdown on the largely peaceful protests against Assad's regime since the uprising began. Most were killed in shootings by security forces on anti-government rallies.

Hama, about 210 kilometres north of the capital Damascus, has become one of the hottest centres of the demonstrations, with hundreds of thousands protesting every week in its central Assi Square.

In early June, security forces shot dead 65 people there. Since then it has fallen out of government control, with protesters holding the streets and government forces ringing the city and conducting overnight raids.

The city has a history of dissent against the Assad dynasty. In 1982, Assad's late father, Hafez Assad, ordered his brother to quell a rebellion by Syrian members of the conservative Muslim Brotherhood movement. The city was sealed off and bombs dropped from above smashed swaths of the city and killed between 10,000 and 25,000 people, rights groups say.

The real number may never be known. Then, as now, reporters were not allowed to reach the area.