Human Rights Watch said it was investigating the same rebel group that claims it has captured UN peacekeepers for executing captured Syrian soldiers earlier this week.
Peter Bouckaert of the human rights monitoring group said it was investigating the involvement of the "Martyrs of Yarmouk" brigade in a video showing the execution of detained Syrian soldiers posted on the Internet yesterday.
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Another unsettled day with cloud, rain and blustery winds.
Buried here are the men of the 10th West Yorks, the unit that suffered the heaviest losses on the first day of the Somme.