At least 300 fighters, primarily from Iraq's Badr and Nujabaa groups, crossed late on Sunday using a dirt road to avoid the official border crossing, two Iraqi security sources said, adding that they were there to defend a Shi'ite shrine.

The sources told Reuters that Hezbollah had not yet been asked to intervene, adding that the group was not ready to send forces to Syria at this stage following more than a year of hostilities against the Israeli military, including two months of heavy ground fighting in southern Lebanon.

Time and time again the Assad dynasty has survived internal and external challenges and lived to fight another day. But nothing lasts forever.