The US has launched strikes to "eliminate ISIS fighters, infrastructure, and weapons sites" in Syria, according to defence secretary Pete Hegseth.
A US official described it as "a large-scale" strike that hit 70 targets in areas across central Syria that had IS infrastructure and weapons.
"This is not the beginning of a war - it is a declaration of vengeance. The United States of America, under President Trump's leadership, will never hesitate and never relent to defend our people," Mr Hegseth said in a social media post.
The announcement came after three US citizens - two National Guard members and a civilian interpreter - were killed in an attack in the Syrian desert on 13 December. Three US personnel were also wounded, the Pentagon's chief spokesperson said on X.
Donald Trump blamed the killings on Islamic State fighters.
"Because of ISIS's vicious killing of brave American Patriots in Syria, whose beautiful souls I welcomed home to American soil earlier this week in a very dignified ceremony, I am hereby announcing that the United States is inflicting very serious retaliation, just as I promised, on the murderous terrorists responsible," President Trump wrote on Truth Social.
"We are striking very strongly against ISIS strongholds in Syria, a place soaked in blood which has many problems, but one that has a bright future if ISIS can be eradicated."
He said the Syrian government was fully supportive of the US strikes against the Islamic State, warning that fighters "will be hit harder than you have ever been hit before".
A US official said the US strike on Islamic State fighters on Friday was conducted using F-15 Eagle jets, A-10 Thunderbolt ground attack aircraft and AH-64 Apache helicopters.
The official, who spoke on condition of anonymity to discuss sensitive operations, said more strikes should be expected.
(c) Sky News 2025: US launches 'large-scale' strikes to 'eliminate' Islamic State fighters in Syr
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