The death toll from airstrikes by US-led forces on the northern Syrian province of Aleppo rose to 52 including seven children, a monitoring group said on Saturday.

The Syrian Observatory for Human Rights said it was the highest civilian loss in a single attack by US and Arab forces since air raids began against jihadists in Syria, including the "Islamic State" (IS) group.

Coalition forces are also targeting IS in Iraq.

The British-based observatory posted a link on social media, reporting that at least 13 people were still missing.

The group claimed the raid had mistakenly struck civilians in a village on the eastern banks of the Euphrates River in Aleppo province.

Members of at least six families were reported to have been killed.

The coalition air strikes have had little impact on IS, as they had slowed the hardline group's advances, but failed to weaken it in the areas it controlled, according to Reuters.

IS had built its own government in Syria's city of Raqqa, where it was most powerful.

Washington said it takes reports of civilian casualties from the US-led strikes seriously and investigates each allegation.

Four years into Syria's civil war a third of the population had been displaced and some 220,000 people killed.

lw/jil (Reuters, dpa)