Aerial bombardments in Syria carried out by the international coalition against "Islamic State" (IS) saw the highest civilian death toll for a single month since they began in September 2014, a group monitoring the Syrian conflict said on Friday.

The airstrikes left 472 civilians dead between May 23 and June 23, more than double the number killed in the previous 30-day toll (225 civilians), the Syrian Observatory for Human Rights said. The death toll included 137 children.

Key IS areas struck

The Observatory said the IS-held provinces of Deir Ezzor and Raqqa were the worst affected, with 222 civilians - including 84 children - killed in Deir Ezzor, along with 250 civilians - including 53 children - in Raqqa.

The latest toll brought to 1,953 the number of civilian deaths from the US-led airstrikes in Syria, it said. The Observatory bases its reports on information gathered by a network of activists on the ground.

Read more: Raqqa - The human cost of degrading the 'Islamic State'

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Bombing intensified

In recent months, the US-led coalition has stepped up bombing of Syrian areas under IS's control. The intense bombardment backs an ongoing campaign by US-allied Syrian fighters seeking to capture Raqqa from the jihadists.

Last month, US Defense Secretary Jim Mattis said President Donald Trump had instructed the Pentagon to "annihilate" IS in Syria in a bid to prevent foreign fighters from returning home.

The coalition insists it takes every measure to avoid hitting civilians, but in its most recent report, it admitted it had "unintentionally killed" 484 civilians recently in both Iraq and Syria. But observers say the number is much higher.

In May, the United Nations accused the US-led alliance of not taking adequate care to prevent civilian deaths in Syria.

The coalition has also come in for severe criticism for hitting civilians during an aerial bombing in the Iraqi city of Mosul in March. More than 100 civilians were killed in a single strike, leading to a temporary halt of the offensive.

mm/tj (AFP, dpa)