BAGHDAD, Iraq — Local ground forces backed by U.S.-led military aircraft launched an operation Monday to storm the ISIS stronghold of Fallujah, officials told NBC News.
The advance marks the latest in a series of attempts to dislodge ISIS militants who have controlled Fallujah, 40 miles west of Baghdad, for more than two years.
An Iraqi military spokesman said an operation to retake the center of the city began at 5 a.m. Monday local time (10 p.m. Sunday ET).
"Our forces now are fighting on the front lines of Fallujah and they are advancing steadily into their targets," Sabah Nua'man, spokesman for the country's counter-terrorism forces, said. "No one can tell now when our forces will be able to liberate the city — this depends on many conditions our forces might face on the ground."
He said aerial coverage of the operation was provided by the Iraqi Air Force and jets from the U.S.-led coalition.
About 50,000 civilians remain inside the city and risk being turned into human shields, Lise Grande the U.N. Humanitarian Coordinator for the country, said Saturday.
The latest assault was launched after Shiite militias and the army's 14th Division advanced from north of Fallujah and liberated the village of al-Sheha, the military's media arm said separately.
It comes less than a week after a U.S. airstrike killed a local ISIS leader in the area. U.S. Army Col. Steve Warren said Maer a-Bilawi was killed in a strike on the group's local headquarters.
Fallujah was the first Iraqi city to fall to ISIS in January 2014. Retaking it promises to be a major challenge for the country's beleaguered security forces.
Separately, several people were killed when militants unleashed a wave of bombings targeting commercial areas in and around Baghdad Monday, police told NBC News.
A car bombing close to the Shalal market in the northern district of Sha'ab killed five residents and injured 15 while a suicide attacker riding a motorbike killed three Iraqi soldiers and wounded six others in Sadr City, a Shi'ite area of eastern Baghdad. The overall death toll could be as high as 24, according to The Associated Press.
This story first appeared on NBCNews.com.