A suicide bomber detonated his bomb-rigged truck near a primary school in a Syrian Shiite town, killing at least six people on Sunday as government military aircraft dropped barrels laden with explosives over residential areas in the north, activists said.

The suicide truck bombing occurred outside a compound of schools in the town of Umm al-Amed in the eastern province of Homs, an official from the governor’s office said. He said the blast destroyed a series of buildings, and that rescue operations were continuing in the area.

Rami Abdurrahman of the British-based Syrian Observatory for Human Rights said at least six people, including children, were killed in the blast. He said he couldn’t say how many of the dead were children.

The governor’s office official said at least 10 people died in the blast, including five students. It wasn’t possible to immediately reconcile the conflicting death tolls. The Observatory obtains its information from a network of activists on the ground.

The bombing underscores how Syria’s civil war, now in its third year, has become increasingly sectarian.

Syria’s rebels are mainly Sunni, with hard-line Muslim brigades emerging as the most powerful fighting groups. Shiites and other Syrian minority groups have either stayed neutral or sided with President Bashar al-Assad, fearing for their future should the uprising prevail. All have killed civilians.

Meanwhile, government forces continued bombing opposition-held parts of the northern city of Aleppo and its surrounding province with barrel bombs for the eighth day. Syrian military helicopters hurled four barrel bombs that exploded in a hardscrabble secondhand market in the rebel-held Masaken Hanano quarter, activists said.

“The medics say they are removing people in parts; they aren’t sure how many they are,” said Hassoun Abu Faisal, an activist with the Aleppo Media Center. He said the bombs destroyed vehicles lining a main road, destroyed a two-storey building and left a crater where part of the market was.

Three members of the same family were killed in the nearby town of Marea after a barrel bomb exploded near a school used by Syrians fleeing fighting in other areas, said Abu Faisal and the Syrian Observatory.

The barrel bombs containers containing hundreds of kilograms of explosives and fuel are wildly inaccurate. Human rights groups warn that even if Syrian forces are targeting rebels with the bombs, they often explode in residential areas, killing civilians.

The aid group Doctors Without Borders says the strikes have killed some 190 people.

Syrian officials have not commented on the air raids in Aleppo, the country’s largest city, and a major front in the war since the rebels launched an offensive there in mid-2012. The city has been carved into opposition- and government-held areas.

The escalation comes ahead of peace talks scheduled to begin on January 22 in Switzerland. The timing has sparked speculation that Mr. Assad may be trying to strengthen his position on the ground and expose opposition weaknesses before sitting down at the negotiating table.

Syria’s civil war, now into its third year, has killed more than 120,000 people, according to activists. Millions have fled their homes because of the fighting.

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