Updated on December 28 at 12:11 p.m. ET

Iraqi government troops, backed by some Sunni tribesman and U.S. airstrikes, have retaken the strategically vital city of Ramadi from the Islamic State group.

“The security forces have entered the governmental buildings and raised the Iraqi flags over them after killing many ISIS militants, and the rest have escaped,” Brigadier-General Yahya Rasool, an Iraqi military spokesman, said.

Colonel Steve Warren, a spokesman for the U.S. military operation against the Islamic State, tweeted an image of the Iraqi flag being raised over the government complex in Ramadi:

RAMADI SUCCESS: Coalition drone video shows ISF raising Iraqi flag over the Ramadi gov't complex. pic.twitter.com/5NYweMXmAU — COL Steve Warren (@OIRSpox) December 28, 2015

Iraqi troops had encircled the city last month, but progress was slow. Militants had booby-trapped bridges leading to Ramadi and had positioned snipers in key areas. The operation to retake the city began last week with about 10,000 Iraqi troops, Sunni tribal fighters, and U.S. airstrikes launching an offensive against ISIS, another name for the Islamic State group. By Monday afternoon, as Rasool put it, Ramadi was “fully liberated” after ISIS fighters fled the government headquarters.