COMPULSORY military service, no public internet access and no way to leave.

Islamic State has reportedly begun fortifying its de facto capital, aiming to officially separate the Syrian city of Raqqa from the rest of the world.

The militant group is preparing its stronghold for an imminent backlash from international military forces in the wake of the Paris attacks, which IS has claimed credit for.

France has redoubled its efforts to battle the terror outfit in Syria, on Monday deploying jets targeting Raqqa, and dozens of US special operations forces are due to arrive in Syria “very soon”.

media_camera A Russian Su-24M during a Russian air raid in Syria. Picture: Russian Defense Ministry Press Service/AP

media_camera A French army jet taking off from a site in Jordan to strike at Islamic State group targets Sunday. Picture: French Army Communications Audiovisual office (ECPAD)/AP Photo

The deployment marks the first official deployment of US troops on the ground since a US-led international coalition was formed to counter the extremist group.

The primary mission of the US troops, special envoy Brett McGurk told CBS, is “focused on isolating the capital of ISIL in Raqqa”.

The coalition is also trying to cut off access for IS to the Syrian border in order to cut off the main access route between Raqqa and the Iraqi city of Mosul and has so far been successful in cutting off one its major supply routes, McGurk explained.

Defeating ISIS: Challenges of Building a Global Alliance In the wake of the Paris attacks, French President Francois Hollande is traveling to Washington and Moscow to build support for a new "grand coalition" to defeat Islamic State. As WSJ's Shelby Holliday reports, the future of Syrian President Bashar al-Assad could stand in the way.

The response from IS has been to bunker down in its stronghold, with reports from within saying militant forces had cut connections for civilians in Raqqa with the outside world.

Activist group ‘Raqqa is being Silently Slaughtered’ (RBBS), which communicates news from inside Raqqa separate to IS propaganda, recently reported IS had upped its conscription efforts demanding all people over the age of 14 register with IS.

media_camera Militant IS fighters and civilians in Raqqa have been cut off from the rest of the world by IS. Picture: Reuters (file)

The call follows the bombardment of Raqqa and its outskirts by France and Russia in retaliation for the Paris attacks and Russian plane bombing, which killed at least 33 IS fighters in three days of air strikes last week.

Associated Press reports the group has responded to the Syrian assault by preventing citizens from leaving Raqqa in order to use them as “human shields”.

RBBS says the group has cut off communication to the outside world, closing internet cafes and preventing the transmission of wireless networks — a decision particularly unpopular with foreign fighters who have travelled to Syria.

The Independent reported defensive bunkers and tunnels are being built around Raqqa.

Russia, France Launch Retaliatory Strikes on ISIS in Syria Russia and France conducted airstrikes against Islamic State targets inside Syria in retaliation for terrorist attacks. The U.S. also launched its own bombing runs. But it's unclear how all these missions will be coordinated.

Originally published as IS readies greatest stronghold