Syrian Kurdish-led forces said Thursday they had launched an offensive against ISIS group fighters, days after jihadist gunmen launched a deadly prison attack.

Six Kurdish fighters were killed Monday when ISIS militants attacked a complex in Raqa, the extremist group’s former de facto capital in Syria, in a bid to free fellow militants imprisoned there.

The Kurdish-led Syrian Democratic Forces said the offensive, dubbed “Operation al-Jazeera Thunderbolt”, aimed to “eliminate” ISIS gunmen from areas that had been “the source of the recent terrorist attacks”.

The SDF said the operation was being carried out alongside the US-backed coalition, although there was no immediate confirmation from the international force that they were taking part.

The SDF statement said that in addition to the thwarted Raqa attack, ISIS fighters had recently carried out eight assaults in the northern Syrian areas of Deir Ezzor, Hasakeh and the Al-Hol camp for displaced people, which houses family members of ISIS militants.

Referencing recent Turkish airstrikes on Kurdish forces in northeast Syria, the SDF said ISIS was trying to “take advantage” of the situation by “carrying out more terrorist attacks”.

After a meteoric rise in Iraq and Syria in 2014, ISIS saw its so-called caliphate collapse, but fighters remain.

Supported by an international anti-extremist coalition led by the United States, the SDF spearheaded the fight against ISIS in Syria and drove the group from its last stronghold in the country in 2019.

ISIS continues to claim attacks in Iraq and Syria, and the SDF regularly launches operations against the extremists in Syria.

The group said Monday’s attack on Raqa aimed to avenge prisoners and female relatives of extremists living in Al-Hol camp.

In September, Kurdish authorities arrested more than 200 people in Al-Hol following the discovery of tunnels and an arsenal of weapons used by extremists.