Amman, Reuters—Air strikes by a US-led coalition set up to fight the Islamic State of Iraq and Syria (ISIS) targeted the Al-Qaeda-linked Al-Nusra Front in northwest Syria overnight, an organisation that tracks violence in the Syrian civil war reported on Thursday.

The Syrian Observatory for Human Rights said the air strikes targeted an office and a vehicle used by Al-Nusra Front in Idlib province in northwestern Syria, where last week the Al-Qaeda-affiliated group routed Western-backed Syrian rebels.

The Observatory also reported the first air strikes against Ahrar Al-Sham, another hardline Islamist insurgent group.

Rami Abdulrahman, head of the Observatory, said it marked the second time Al-Nusra Front has been hit in the US-led campaign. The first was on September 23—the first day of the US air strikes in Syria that are part of Washington’s strategy to “degrade and destroy” ISIS.

The United States said that attack had targeted Al-Qaeda veterans which it referred to as the Khorasan group.

Al-Nusra Front last week seized control of areas of Idlib province from Western-backed rebel leader Jamal Maarouf, head of the Syria Revolutionaries Front in northern Syria, confiscating its weapons. It also took positions from the Hazzm movement, another recipient of Arab and Western support.

It marked a big blow to the non-Islamist opponents of President Bashar Al-Assad who have generally struggled against better armed and equipped Islamist groups including Al-Nusra Front and ISIS.

The United States is planning to expand military support to what it describes as the moderate opposition to Assad as part of its strategy against ISIS in Syria.

Al-Nusra Front was once seen as the strongest insurgent group in Syria but has been eclipsed this year by ISIS, which has seized wide areas of northern and eastern Syria.