The Syrian Observatory for Human Rights says government air raids have killed nearly 2,000 civilians this year in and around Aleppo, the country's largest city.
Images from Aleppo

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Men gather at a site hit by what activists said was a barrel bomb dropped by forces loyal to President Bashar al-Assad, in al-Qarlaq, Aleppo, May 29, 2014.

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Rescue workers, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb dropped by forces loyal to President Bashar al-Assad, al-Qarlaq, Aleppo, May 29, 2014.

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Rescue workers, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb dropped by forces loyal to President Bashar al-Assad, al-Qarlaq, Aleppo, May 29, 2014.

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A man holds a wounded child in a building hit by what activists said was a barrel bomb dropped by forces loyal to President Bashar al-Assad, Bustan al-Qasr, Aleppo, May 28, 2014.