U.S. intelligence officials have said that at least 2,000 ISIS insurgents are still holed up in the Syrian city of Raqqa fighting for their lives as a U.S.-led coalition closes in on the city.

According to U.S. counter-terror special envoy Brett McGurk, thousands of fighters still remain in the city and are using the estimated 25,000 civilians on the ground as human shields.

“We think there’s about 2,000 ISIS fighters left in Raqqa, and they will – they most likely will die in Raqqa,” he said.

“And what’s really happening in Raqqa – similar to what we saw in Mosul but on a smaller scale – the ISIS fighters on the ground are using these civilians as their own shields, as their own hostages. They are using snipers to kill civilians who are trying to escape.”

He noted that the terrorists are trying to put suicide bombers in columns of displaced people as they try to get out.

According to U.S. officials, ISIS had 40,000 foreign fighters in Syria and Iraq in 2014 from 110 countries.

Since then, ISIS is believed to have lost 70,000 square kilometers of territory – 78 percent of the territory they used to hold in Iraq, and 58 percent of the territory they used to hold in Syria.