BEIRUT/BAGHDAD (Reuters) – Syria’s army and its allies began an assault on the largest remaining stronghold of Islamic State in Syria and Iraq on Wednesday, Hezbollah-controlled media said, signaling the imminent fall of the militant group’s self-proclaimed caliphate.

Islamic State has been all but destroyed over the past two years, remaining only in Albu Kamal in Syria, Rawa in Iraq, in a few neighboring villages and patches of desert, and some isolated pockets elsewhere.

At the height of its power in 2015, it ruled over an expanse of the two countries, eradicating their border, printing money, imposing draconian laws and plotting attacks across the world.

On Wednesday, the army and its allies surrounded Albu Kamal and started to enter it, the pro-Hezbollah al-Manar television said. The Syrian Observatory for Human Rights, a British-based war monitor, reported that Iraqi militias had crossed into Syria to join the assault, but they denied it.

Despite its losses, Islamic State still has a territorial presence in Libya and elsewhere, and many governments expect it to remain a threat even after it loses the caliphate it declared from Mosul, Iraq, in 2014.

It has already carried out a series of guerrilla operations in both Iraq and in Syria, and it has continued to inspire lone militants to attack civilian targets in the West.

In Syria, the end of major battle operations against Islamic State may only prefigure a new phase of the war, as the rival forces which have seized territory from the jihadists square off.

The Syrian army, alongside its Lebanese ally Hezbollah and other Shi‘ite militias, and backed by Iran and Russia, have seized swathes of central and eastern Syria in an advance against Islamic State this year.

Russian official media have in recent weeks reported a surge of strategic bombing and cruise missile strikes on Islamic State targets in eastern Syria as the army advanced.

A U.S.-backed coalition has supported a rival campaign in Syria by the Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab militias that have pushed Islamic State from much of the country’s north and east.

NEW PHASE

The Syrian government has sworn to recapture territory held by the SDF, including Islamic State’s former capital Raqqa and oil and gas fields lying east of the Euphrates.

In areas controlled by the SDF in northern Syria, Kurdish-led groups have established autonomy, announcing elections and setting internal policies.

On Tuesday, Bouthaina Shaaban, a senior adviser to Syrian President Bashar al-Assad, described the U.S. forces aiding the SDF in Syria as illegal invaders. Washington has not spelled out how its military support for the SDF would evolve after Islamic State’s defeat.

Shaaban also pointed, in a television interview, to the example of Iraq, where the government retaliated against an autonomous Kurdish region after it held an independence referendum.

Iraqi military officials say small groups of Islamic State militants are still entrenched in the town of Rawa and the border desert strip with Syria. Scattered villages near al-Qaim, close to Albu Kamal, are still under militant control in an area called Rummana.

The Iraqi Popular Mobilisation Forces (PMF), an alliance of militias, denied a report by the Observatory that it had crossed the Syrian border and was attacking Albu Kamal.

“Our movements are carried out under orders from the commander in chief of the armed forces and our key objective is to liberate Iraq’s territories from Daesh. We have no orders to cross the borders,” PMF spokesman Ahmed al-Asadi said.