BEIRUT (Reuters) - A convoy of Islamic State fighters and their families being evacuated into jihadist territory in east Syria remained in government-held areas of Syria on Friday, U.S.-led forces said.   It has not managed to link up with any other ISIS elements in eastern Syria,  said Colonel Ryan Dillon, spokesman for the U.S.-led coalition fighting Islamic State.  There are about 300 fighters and about 300 civilians in the convoy, which the Syrian army and Lebanon s Hezbollah group granted safe passage after the jihadists surrendered their enclave on Syria s border with Lebanon. But the coalition against Islamic State has used air strikes to block the convoy from crossing into the group s main territory straddling Syria s eastern border with Iraq. The Islamic State fighters in the border pocket accepted a truce and evacuation deal after simultaneous but separate offensives by the Lebanese army on one front and the Syrian army and Hezbollah on the other. It angered both the coalition, which does not want the fighters bussed to a battlefront in which it is active, and Iraq, which is fighting Islamic State across the border.   We are continuing to monitor that convoy and will continue to disrupt its movement east to link up with any other ISIS element and we will continue to strike any other ISIS elements that try to move toward it,  Dillon said.  The coalition has asked Russia to tell the Syrian government that it will not allow the convoy to move further east to the Iraqi border, the coalition said in a statement.  Syrian President Bashar al-Assad gave prayers on Friday for Islam s Eid al-Adha festival in the town of Qara, near the enclave surrendered on Monday by the Islamic State fighters. Confined to Damascus for long periods in the early part of Syria s six-year civil war, Assad has grown more confident in traveling around government-held areas as the army and its allies have won a series of victories.  Assad was shown on state television standing and kneeling on a green carpet in a packed mosque alongside Syrian religious leaders as he followed the imam giving prayers.  The departure of Islamic State and other groups from the Western Qalamoun district means the border with Lebanon is Syria s first to be controlled entirely by its army since early in the conflict.  Qara is only a few miles from the mountains delineating the frontier with Lebanon, in which Islamic State and other militant groups held territory until August.  Part of an agreed exchange under the truce went ahead on Thursday as wounded Islamic State fighters were swapped for the bodies of pro-government forces. But the fate of the main part of the convoy is uncertain.  It was moving this morning and then they had stopped. ... I don t know if they stopped for a break or were trying to figure out what to do,  Dillon said.  The frontline between Syrian government forces and Islamic State in eastern Syria is active, as the army, aided by Russian jets and Iran-backed Shi ite militias, presses an offensive to relieve its besieged enclave at Deir al-Zor.  On Friday, a Syrian military source said the army and its allies had made an advance against Islamic State in that area and had also taken several villages in a jihadist enclave in central Syria. 