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.

Defence Secretary Pete Hegseth said Operation Hawkeye Strike was aimed at eliminating IS fighters, infrastructure, and weapons sites.

Fighter jets, attack helicopters and artillery hit multiple targets in central Syria, US officials told CBS, the BBC's media partner in the US. Aircraft from Jordan were also involved.

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

In a post on X late on Friday, Hegseth wrote: 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.

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.

Meanwhile, the US Central Command (Centcom) said that US forces have commenced a large-scale strike against IS, adding that more information would be provided soon.

Posting on Truth Social later, President Trump said the US is inflicting very serious retaliation, just as I promised, on the murderous terrorists responsible and mentioned that the Syrian government was fully in support.

The UK-based Syrian Observatory for Human Rights (SOHR) reported that IS positions near the cities of Raqqa and Deir ez Zor were targeted, claiming that a prominent IS leader and several fighters were killed.

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

Centcom, which directs American military operations in Europe, Africa and the Indo-Pacific, earlier indicated 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, happening in an area where the Syrian president does not have control, according to a Pentagon official.

Simultaneously, the SOHR indicated that the attacker was a member of the Syrian security forces.

No group has claimed responsibility for the ambush, and the identity of the gunman remains undisclosed.

IS was declared territorially defeated in Syria in 2019, but the group is believed to have between 5,000 and 7,000 fighters still active in the region.

US troops have maintained a presence in Syria since 2015 to assist in the fight against IS.