The US says its military has carried out a "massive strike" against the Islamic State group (IS) in Syria, in response to a deadly attack on American forces in the country.

The US Central Command (Centcom) said fighter jets, attack helicopters and artillery "struck more than 70 targets at multiple locations across central Syria". Aircraft from Jordan were also involved.

It said the operation "employed more than 100 precision munitions" targeting known IS infrastructure and weapons sites.

President Donald Trump said "we are striking very strongly" against IS strongholds, following the 13 December IS ambush in the city of Palmyra in which two US soldiers and a US civilian interpreter were killed.

In a statement on X, Centcom, which directs American military operations in Europe, Africa and the Indo-Pacific, said Operation Hawkeye Strike was launched at 16:00 Eastern Time (21:00 GMT) on Friday.

Centcom commander Admiral Brad Cooper said that the US "will continue to relentlessly pursue terrorists who seek to harm Americans and our partners across the region".

US Defence Secretary Pete Hegseth said the operation "is not the beginning of a war - it is a declaration of vengeance.

"If you target Americans - anywhere in the world - you will spend the rest of your brief, anxious life knowing the United States will hunt you, find you, and ruthlessly kill you.

"Today, we hunted and we killed our enemies. Lots of them. And we will continue," the US defence secretary added.

Posting on Truth Social, President Trump said the US "is inflicting very serious retaliation, just as I promised, on the murderous terrorists responsible".

He said the Syrian government was "fully in support".

Meanwhile, the UK-based Syrian Observatory for Human Rights (OBHR) said IS positions near the cities of Raqqa and Deir ez Zor were targeted.

It said that a prominent IS leader and a number of fighters were killed.

IS has not publicly commented. The BBC was unable to verify the targets immediately.

Centcom earlier said that the deadly attack in Palmyra was carried out by an IS gunman, who was "engaged and killed".

Another three US soldiers were injured in the ambush, with a Pentagon official saying that it happened "in an area where the Syrian president does not have control."

At the same time, the SOHR said the attacker was a member of the Syrian security forces.

No group has claimed responsibility for the attack, and the identity of the gunman has not been released.

In 2019, a US-backed alliance of Syrian fighters announced IS had lost the last pocket of territory in Syria it controlled, but since then the jihadist group has carried out some attacks.

The United Nations says the group still has between 5,000 and 7,000 fighters in Syria and Iraq.

US troops have maintained a presence in Syria since 2015 to help train other forces as part of a campaign against IS.

Syria has recently joined an international coalition to combat IS and has pledged to co-operate with the US.

In November, Syrian President Ahmed al-Sharaa - a former jihadist leader whose coalition forces toppled Bashar al-Assad's regime in 2024 - met Trump at the White House, describing his visit as part of a "new era" for the two countries.