BEIRUT (Reuters) - Syria s army and its allies neared al-Mayadin on Friday, sources said, pushing an advance on an eastern city seen as Islamic State s main remaining base in the country. The government forces had reached within 10 km (7 miles) of the city and taken positions parallel with a key road, a military media unit run by the Lebanese Hezbollah group said . The Syrian Observatory for Human Rights, a war monitor, said the army supported by Russian forces had reached the western edge of al-Mayadin, entering the ruins of a castle and an area of grain silos. Islamic State has lost swathes of territory in recent months  to the Syrian government, backed by Russian air power and Iran-allied militias, in eastern Deir al-Zor province that borders Iraq. A Syrian military source told Reuters fighting was ongoing around Deir al-Zor towards al-Mayadin on Friday.   The Syrian army is continuing to strike the terrorist Daesh (Islamic State) group fiercely in Deir al-Zor and its surroundings ... and will continue its operations until it eliminates (Daesh) and drive what s left of them out of this province,  he said. Last month the Syrian army s advance to Deir al-Zor city lifted a three-year-long siege imposed by Islamic State on a government-held enclave there. The army has since pushed its advance further eastwards towards al-Mayadin, which lies 45 km south of Deir al-Zor, along the Euphrates valley.   U.S.-backed Syrian militias are also waging a separate campaign against the jihadist group s last major strongholds in Deir al-Zor province   In June, two U.S. intelligence officials told Reuters that they believed Islamic State had moved most of its diminished command structure and propaganda team to al-Mayadin, southeast of its former capital of Raqqa. The Observatory said on Friday there were clashes in several areas in eastern Deir al-Zor province. The Syrian military shelled al-Mayadin overnight and Syrian and Russian warplanes have conducted hundreds of strikes, it said.  Hezbollah, part of the military alliance supporting President Bashar al-Assad, said this week a senior commander had been killed in an Islamic State attack in Syria s central desert. 
Syrian army nears Islamic State stronghold al-Mayadin