Heavy Russian air strikes hit ISIS-held territory in eastern areas of Syria’s Hama province, near the boundary of Raqqa province.

The Syrian army has crossed the boundary of Raqqa province after advancing in a major Russian-backed offensive against ISIS militants, the Syrian Observatory for Human Rights, a group that monitors the war, said on Saturday.

Heavy Russian air strikes hit ISIS-held territory in eastern areas of Syria’s Hama province, near the boundary of Raqqa province, on Friday and the army reached the edge of the province.

Raqqa city, further east, is ISIS’s de facto capital in Syria and, along with Mosul in Iraq, the ultimate target of those seeking to destroy the group’s self-declared caliphate.

Syrian army spokesmen were not immediately available for comment.

The Syrian army offensive is the third big assault on the self-proclaimed caliphate in recent days after Iraqi forces attempted to storm a city and a Syrian militia advanced with US support.

The three big offensives are some of the most aggressive campaigns against ISIS since it declared its aim to rule over all Muslims from parts of Iraq and Syria two years ago.

Related articles across the web

• Russian Warplanes In Syria Bomb Strategic Road In Aleppo
• Russia bombs strategic road in Syria's Aleppo
• Monitor, Rebels: Heavy Airstrikes Hit Rebel Road to Syria's Aleppo
• Updated: Bombings against civilians kill 148 in government-held coastal Syria
• Isil targets commuters as 78 die in bus station explosions
• Syria rebels set 48-hour deadline to end regime assault
• Syria blames Turkey, Qatar, Saudi Arabia for deadly bombings
• Syria blames Turkey, Qatar and Saudi Arabia for deadly bombings - BBC News
• Watchdog: Over 400 Civilians Killed in US Airstrikes on Syria
• Pressure mounts on ISIS with twin assaults in Iraq, Syria