Damascus - The Syrian army has laid full siege on areas under the control of the Islamic State (ISIS) in the eastern countryside of Hama and Homs provinces in central Syria, a military source told Xinhua on Friday. The ISIS militants have become besieged in an area of 3,000 sq km in the eastern countryside of Homs and Hama provinces after the advancing troops met in the Fasdeh mountain in eastern Hama from two directions: the southern part of Athria in eastern Hama countryside and al-Shaer area in eastern Homs countryside. The operation has been carried out over the past 48 hours, as part of the ongoing military operation against ISIS in the Syrian desert, the source told Xinhua on condition of anonymity. Meanwhile, the Syrian Observatory for Human Rights said Friday that the Syrian army progress in the eastern countryside of Homs enabled the troops to capture around 1,000 sq km from ISIS. The progress also allowed the army to capture around six gas fields in the Syrian desert, some 80 km southwest of Tabqa city in Raqqa province countryside, near the borderline between Homs and Hama. The Observatory, which says it relies on a network of activists on the ground, said the Russian air force was heavily backing the Syrian ground troops in their push against ISIS in that part of the country.