"The strikes against the ISIS leaders, operatives and camps were conducted as part of the ongoing mission to disrupt, degrade and defeat ISIS," US Central Command (CENTCOM) said on social media, using an acronym for the Islamic State group.

The aim is to prevent "the terrorist group from conducting external operations and to ensure that ISIS does not seek opportunities to reconstitute in central Syria," CENTCOM said.

"These recent strikes are in former regime and Russian-controlled areas ensuring pressure is maintained on ISIS," it added.

Washington is seeking to prevent the jihadist group from taking advantage of the fall of Bashar al-Assad's government, which was overthrown by an Islamist-led rebel alliance that took the capital Damascus on December 8.

That day, US forces hit more than 75 targets associated with the Islamic State group in Syria using a combination of warplanes including B-52s, F-15s, and A-10s.

The US military has around 900 troops in Syria and 2,500 in Iraq as part of an international coalition against the Islamic State group that was established in 2014 to combat the jihadists.