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Rebels have killed dozens of Shiite Muslims in a village in eastern Syria, activists said Wednesday, as the nation’s drawn-out civil war takes on increasingly sectarian undertones.

About 60 civilians and pro-government fighters were killed Tuesday as rebels stormed the largely Shiite village of Hatla in Deir al-Zour province, near the Iraqi border, according to the Britain-based Syrian Observatory for Human Rights. Videos released by the activist group showed rebels boasting of burning the houses of “rejectionists,” a derogatory term for Shiites.

As the conflict enters its third year, it has become increasingly divided along sectarian lines, pitting a largely Sunni opposition against Shiites and Alawites, the offshoot of Shiite Islam to which President Bashar al-Assad belongs. That shift was evident in the battle for the border town of Qusair earlier this month, where militants from the Lebanese Shiite movement Hezbollah led the offensive with Assad’s troops.

Feeding into a larger Shiite-Sunni struggle in the region, the war is transcending Syria’s borders. In Lebanon on Wednesday, the Lebanese army said a Syrian helicopter fired rockets into the largely Sunni border town of Aarsal, injuring at least two people. The town has supported the Syrian uprising.

“For the first time, we really feel like we are part of the reality of what is going on in Syria,” said Wafic Khalaf, a member of the town’s municipal council. “People were scared.”

Timeline: Major events in Syria’s tumultuous uprising that began in March 2011.

Rockets fired by the Syrian air force have fallen near Aarsal before, but never inside the town’s perimeter. On Wednesday, one fell 100 yards from the municipality building, hitting an abandoned building, Khalaf said. Another fell 200 yards away, sending shrapnel flying, he said.

The attack on Aarsal followed claims by Hezbollah supporters that the town’s residents had fired rockets into Shiite areas of Lebanon’s Bekaa Valley.

The killings in Hatla, in Deir al-Zour, were the result of “violent clashes and rebel bombardment,” the Syrian Observatory said, adding that rebels had attacked the village after pro-government fighters tried to seize a rebel position the day before. Ten rebels were killed in the offensive, the group said.

One video posted by the rights group shows a group of bearded men carrying black flags. “The heroes and men of the city of Deir al-Zour stormed and burned the houses of Shiites, the rejectionists, who have forsaken their religion,” the cameraman says in the clip.

In another video, the camera pans to blankets laid out on the ground as a man lifts one to reveal a man’s body. “These are the dead of the Shiites . . . God is great,” the cameraman says.

A fighter says in the video: “Oh Sunnis . . . support your religion. Don’t support the Syrian people. Support your religion instead, as we are out to support our religion.”

The videos’ authenticity could not be independently verified.

Thaer al-Deiry, an activist based in Deir al-Zour who used a pseudonym for fear of government retaliation, told the Associated Press that the village had been under opposition control for over a year but that some residents had started to collect arms to fight alongside Assad.

After the attack, about 150 Shiites from the village fled to the nearby government-held village of Jafra, Deiry said.