Over 50,000 civilians are reportedly trapped inside ISIS-controlled Fallujah as Iraqi forces surround the town and prepare for an all-out assault on one of the militant's last major strongholds in the country.

Al Jazeera reported that conditions in the city, under ISIS control since 2014, have deteriorated as fighting between the militants and Iraqi forces has intensified in the past few days.

Some residents have been evacuated, but ISIS checkpoints on the main roads has made it nearly impossible for others to flee the city, Al Jazeera reported.

The spiritual leader of Iraq's Shiites called on Iraqi forces preparing to retake the city to safeguard civilians. Grand Ayatollah Ali al-Sistani said that "saving innocent people from harm's way is the most important thing, even more so than targeting the enemy."

Brigadier Rasool Yahya told the news agency that the presence of the civilians inside the town, about 45 miles west of Baghdad, may delay the assault.

In Baghdad, Iraqi security forces fired tear gas and live ammunition to disperse thousands of anti-government protesters gathered in the city's Tahrir roundabout. The protesters assembled despite calls earlier this week from Iraqi Prime Minister Haider al-Abadi to halt protests so the country's security forces could focus on the Fallujah operation.

The Iraqi forces have been backed by air power from the U.S.-led coalition. It is believed that between 500-700 ISIS fighters remain in the city. 

"Our troops are now in the process of surrounding the city from all (sides)," said Lt. General Abdul-Wahab al-Saadi, the head of the counterterrorism forces' Fallujah operation. "By doing so, we will besiege the city of Fallujah in full. And then we will start storming city from several directions with new forces."

The Associated Press contributed to this report.