Tens of thousands of Syrians marched on Friday, April 13, heeding an opposition call for protests, as clashes between troops and rebels tested a shaky ceasefire in a 13-month crackdown that has killed thousands, Agence France Presse reported. U.N.-Arab League peace envoy, Kofi Annan, who brokered the ceasefire, urged Syria to open humanitarian corridors to deliver aid. Annan and U.N. Secretary General Ban Ki-moon expressed concern about the Syrian government’s history of reneged commitments during the conflict, which has left more than 9,000 people dead. Sporadic clashes broke out between troops and rebel fighters on the northern border with Turkey. Violence on Thursday killed at least 10 people, including seven civilians, and wounded dozens more. On Friday, the U.N. Security Council could vote on a resolution authorizing the deployment of observers to monitor both sides in the conflict.