Story highlights

Opposition group says four high-ranking officers were killed

The attack took place Sunday in a suburb of Damascus

CNN  — 

A bomb attack Sunday against military offices in a suburb of Damascus killed at least 31 Syrian troops, including four high-ranking officers, an opposition group said.

Rebel groups planted the explosives in Harasta, said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

A video posted on YouTube showed a massive explosion and the rapid collapse of a building. CNN could not independently verify the video or opposition account.

State-run media made no mention of the attack.

Syria’s descent into civil war began in March 2011, when President Bashar al-Assad’s regime forcefully cracked down on peaceful anti-government protesters.

That conflict spiraled into an armed uprising and a 2-year-old crisis that the United Nations says has claimed more than 100,000 lives.

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CNN’s Mohammed Tawfeeq and Samira Said contributed to this report.