BEIRUT (Reuters) - Air strikes by US-led forces in Syria have killed 910 people, including 52 civilians, since the start of the campaign against Islamic State and other fighters two months ago, a group monitoring the conflict said on Saturday.

The majority of the deaths, 785, were fighters of Islamic State in Iraq and Syria (ISIS), according to the Britain-based Syrian Observatory for Human Rights. ISIS, a hard-line offshoot of Al-Qaeda, has seized land in Syria and neighbouring Iraq, where it has also been targeted by US-led strikes since July.

Eight of the civilians killed were children and five were women, the Observatory said. The United States has said it takes reports of civilian casualties seriously and says it has a process to investigate any reports of such deaths.

The Observatory, which gathers its information from a network of contacts on the ground, said 72 members of Al-Qaeda's Syria wing Al-Nusra Front were also killed in the air strikes, which started on Sept. 23.

The United States has said it has targeted the "Khorasan Group" in Syria, which it describes as a grouping of Al-Qaeda veterans under the protection of Al-Nusra Front. Most analysts and activists do not differentiate between the groups in this way.

According to the United Nations, around 200,000 people have been killed in Syria's conflict, which is in its fourth year.