The last vestiges of what just a few years ago was proclaimed as the Islamic State’s new ‘caliphate’ is crumbling under constant attack from Iraq’s forces as they push to retake Mosul.

Iraqi military spokesmen say that the ISIS fighters remaining in what is left of their stronghold of Mosul are in a “fight to the death.” Only about 5 percent of the city remains in the hands of the Islamic State as US-backed Iraqi forces continue to keep the pressure on.

Gen. Abdel Ghani al-Asadi, the head of Iraq’s special forces, said his troops were just 250 yards from the Tigris River on Tuesday after retaking the Mosul’s main hospital compound from ISIS the day before.

He said the militants are increasingly resorting to suicide bombings, and he expects the fighting to get even heavier as they are pushed closer to the river.

Iraqi forces launched the operation to retake Mosul, the country’s second largest city, in October.

Brett McGurk, the U.S. envoy to the anti-ISIS military coalition, said Tuesday in a tweet that the militants remained in control of only about a square half-mile of Mosul.

The Iraqi Defense Ministry said two senior ISIS fighters were captured trying to flee from western Mosul to the town of Qayyara in the south. One of them was described as an administrative official and the other was allegedly a top bomb-making expert, according to the Ministry.

Forces from the elite Iraqi Counter-Terrorism Service, the federal police, the regular Iraqi army and the Emergency Response Division have fully surrounded the extremists in the old part of Iraq’s second-largest city and are fighting through the winding, narrow streets to root them out of their remaining entrenched positions.