Violence flared between Lebanon's Hizbollah guerrillas and Israeli troops along the border on Wednesday, raising fears of a widening of the conflict between Israel and its Arab foes. The Syrian-and Iranian-backed Muslim group has launched strikes almost daily since Israel began incursions into Palestinian towns and cities in the West Bank 12 days ago. The United States has expressed "grave concern" over the escalation and the United Nations has asked the Lebanese authorities to stop the clashes that are turning the volatile border area into a hotspot. The Lebanese border has been under the control of Hizbollah since Israel pulled out its troops in May 2000, ending a 22-year occupation.