At least 23 people have been killed and dozens more wounded in a suicide blast in southern Syria near the border with Jordan. <br/><br/>The Syrian Observatory for Human Rights said the bomber detonated an explosive belt yesterday at a base used by Jaish al-Islam near the Nasib border crossing. It said, most of the killed were from Jaish al-Islam.<br/><br/>Observatory head Rami Abdel Rahman said, dozens were wounded in the blast, including 20 in critical condition. <br/><br/>There was no immediate claim of responsibility, but media reports suggests that jihadists linked to the Islamic State group have attacked rebels in southern part of the country.<br/><br/>The Nasib border crossing lies in Daraa province and was captured by rebel groups in April 2015.<br/><br/>Syria's uprising erupted in the province in March 2011 with widespread protests calling for the ouster of President Bashar al-Assad.<br/><br/>It has since turned into an all-out war that has drawn in international powers and killed more than 330,000 people.<br/><br/>Under a plan hammered out in May between Russia, Turkey and Iran at peace talks in Kazakhstan, four "de-escalation zones" were to be established across swathes of Syria to ease<br/>fighting between regime and rebel forces.<br/>