The Syrian opposition delegation threatened to quit the Geneva peace talks, due to resume Monday, as a renewed flare-up in violence in Aleppo killed another 22 civilians.
Syria's main opposition group said it would attend peace talks on Monday but accused the government of President Bashar al-Assad of preparing to escalate the war.
Syrian opposition chief Riad Hijab arrived in Switzerland on Wednesday afternoon, his grouping said, in a move that could rekindle troubled UN-brokered peace talks.
