Iraqi government forces fire a rocket near Sejar village, northeast of Fallujah, on May 26 as they take part in a major assault to retake the city from the Islamic State. (Ahmad Al-Rubaye/AFP/Getty Images)

Civilians trapped in the Iraqi city of Fallujah face mounting threats as humanitarian conditions worsen and Iraqi forces­ press their offensive to oust the Islamic State, local and foreign officials said Thursday.

About 50,000 civilians are believed to remain in the city, which has been under Islamic State control since January 2014, living under the militants’ harsh and capricious rule. Conditions for residents have grown dire in recent months as a siege by government-aligned forces has aggravated shortages of food and medicine.

Now, officials from Fallujah fear that the ongoing operation designed to break the militants’ grip on the city will further endanger civilians. In recent days, a combined force of Iraqi army troops, police, Shiite militiamen and Sunni tribal fighters has made progress in clearing militants from areas around Fallujah, in preparation for a push into the city in western Anbar province.

U.S. planes have provided air support to some government forces­ and tribal groups.

Prime Minister Haider al-Abadi, who visited a military field headquarters just east of Fallujah on Thursday, called on security forces­ to move forward with care.

Iraqi security forces and allied Sunni tribal fighters arrive May 25 to join the forces surrounding Fallujah. (AP)

“The armed forces and the brave fighters, their duty is to protect civilians from this terrorism, from random killing, from torture,” Abadi said.

While ground troops have sought to open pathways for trapped residents, officials said that few have been able to escape.

Officials from Fallujah also said that civilians have been killed by shelling from forces­ outside the city, but the Iraqi military denies those claims.

Abadi’s government has faced criticism for permitting heavy-handed tactics in previous operations against the Islamic State, including in Ramadi, the Anbar provincial capital about 32 miles to the west. This time, the prime minister, grappling with a political crisis and a spate of recent attacks in Baghdad, is determined to limit urban destruction and keep civilians safe.

Fallujah Mayor Issa al-Issawi said the situation inside the city was “indescribable.” Speaking from a nearby town, he said there was little food, medicine, drinking water and electricity left in Fallujah. Officials say militants have restricted distribution of what few goods remain.

Internally displaced civilians from Fallujah flee their homes during a fight between Iraqi security forces and the Islamic State during a military operation to regain control of the city. (AP)

In recent days, the Islamic State, readying for battle, has begun lashing out at residents and has killed several families trying to flee, local officials said. The Washington Post could not independently confirm those reports.

Jasim al-Halbusi, a member of the Anbar provincial council’s security committee, said militants erected blast walls on one of the bridges leading out of the city to keep people in.

He said the Islamic State was not the only factor keeping desperate residents in place.

“Also the families are hesitating to take these exits . . . because they’re afraid of what’s waiting for them on the other side, which are the popular mobilization ­forces,” Halbusi said, referring to the Shiite militias now arrayed outside the city. “They are between two fires.”

Lt. Gen. Mohammed al-Askari, a senior adviser at the Iraqi Defense Ministry, said the presence of civilians would shape decisions about troop movements and the use of fire support as state forces­ advance into the city. The government has not said when that will occur, only that it hopes the operation will be relatively swift.

“It’s going to be a major obstacle, how to secure the civilians, because we care about gaining the trust of the civilians that we are liberating,” Askari said. “This is our main aim.”

Iraq’s highest Shiite religious authority, Grand Ayatollah Ali Sistani, called this week for the protection of civilians, issuing a statement urging fighters to abide by the rules of combat. Sistani wields major influence with Shiite militia groups, whose leaders have said they intend to support the offensive from outside Fallujah.

The government is now scrambling to prepare for what may be an exodus of residents from the city.

According to the United Nations’ humanitarian office for Iraq, 2,000 family tents have been prepared at a camp in nearby Amiriyah Fallujah, and 3,000 more could be erected if needed. Other camps are being readied elsewhere.

Even with outside assistance, the government’s ability to respond has been undermined by a fiscal crisis caused by low oil prices.

Giovanni Bosco, who heads that U.N. office, said the government recently informed U.N. officials that it would need $9 million to provide electricity for camps housing the displaced.

That power “is critical given the very high temperatures during Anbar summers and very cold winter,” Bosco said.