US-led air strikes against the Islamic State of Iraq and the Levant (ISIL) group in Syria have killed more than 1,600 people since they began five months ago, a monitor said.

The Syrian Observatory for Human Rights said on Monday that almost all of those killed were fighters from ISIL and al-Qaeda's Syrian affiliate al-Nusra Front, though it also documented the deaths of 62 civilians.

The Britain-based monitor said the strikes that began on September 23 had killed 1,465 members of ISIL, most of them non-Syrians.

Another 73 fighters from al-Nusra Front were killed, along with a man from a rebel group being held prisoner by ISIL in the group's de facto capital Raqa.

Washington and a small coalition of Arab countries began strikes against ISIL in Syria last year, expanding US-led operations with a broader coalition already under way against ISIL in Iraq.

ISIL emerged in Syria in 2013, growing from al-Qaeda's former Iraqi affiliate.

But it broke with al-Qaeda and declared an Islamic "caliphate" in territory it controls in Syria and Iraq, attracting a steady stream of foreign fighters and carrying out abuses including beheadings.

Source: AFP