The violence came hours after the U.S. slapped new sanctions on Mr. Assad that for the first time hold the Syrian leader personally accountable for attacks by his security forces.

The Syrian army shelled a border town overnight and early Thursday, sparking gun battles that killed at least eight people, and the government condemned U.S. sanctions targeting President Bashar Assad for the brutal crackdown that has killed more than 850 people.

The violence came hours after the U.S. slapped new sanctions on Mr. Assad that for the first time hold the Syrian leader personally accountable for attacks by his security forces.

U.S. President Barack Obama was expected to use a sweeping Middle East speech on Thursday to defend the sanctions and offer stern words for Mr. Assad.

The European Union, meanwhile, is pushing for a second round of European sanctions that would target Mr. Assad.

The Syrian government denounced the U.S. measure, calling it “one in a series of sanctions imposed by the U.S. administration against the Syrian people as part of U.S. regional policies serving Israel.”

The move “did not and will not affect Syria’s independent choices and steadfastness,” Syria’s state—run news agency said.

The statement accused the U.S. of a double standard, saying the U.S. has no respect for human rights in its killing of civilians in Afghanistan, Iraq and Libya. The U.S. has troops in Iraq and Afghanistan and is part of the NATO coalition maintaining a no—fly zone over Libya and trying to protect Libyan citizens from government attacks.

The overnight attack on the border town of Talkalakh killed at least eight people, bringing the death toll to 34 since the military sealed off the border town on Saturday and moved in tanks and troops, two human rights activists told The Associated Press. Syrians fleeing to Lebanon in recent days have described horrific scenes of execution—style slayings and bodies in the streets in Talkalakh.

Syria has banned foreign journalists and prevented coverage of the conflict, making it nearly impossible to independently verify accounts coming out of the country or to gauge the strength of the unprecedented protest movement in one of the most authoritarian regimes in the Middle East.

Talkalakh, a town of some 70,000 people near the border with Lebanon, is known to be a smuggling area where many residents are armed. It has been a hotbed of dissent during the two—month uprising against Assad’s autocratic rule.

One activist, who asked that his name not be used for fear of reprisals from the government, said there were heavy exchanges of fire between security forces and armed civilians. He added that 19 soldiers also have died in the town.

The second activist, Mustafa Osso, said he could not confirm the accounts of armed resistance from civilians. He said his group was investigating reports that security forces were shooting at soldiers who refused to fire on civilians.

A Talkalakh resident who fled across the border to Lebanon said Syrian troops brought reinforcements to the village of Arida outside the besieged town.

“We heard shelling throughout the night and can still hear gunfire every now and then,” he said on Thursday from the border, speaking on condition of anonymity for fear of reprisals.

He said he could see troops patrolling the border and smoke from fires in the town, apparently from homes burning.

The U.S. action marks the first time that sanctions would hold Mr. Assad personally accountable for actions of his security forces.

“The recent events in Syria, we believe, prove that the country cannot go back to the status quo ante,” said White House press secretary Jay Carney. “Syria’s future will only be secured by a government that reflects the popular will of its people.”

But long-time ally Russia threw its support behind Mr. Assad. Russian President Dmitry Medvedev said on Wednesday that Mr. Assad must be given a chance to fulfill his reform promises and warned against foreign interference in the country.

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