A US-led coalition airstrike on the city of Raqqa in Syria resulted in the deaths of 43 civilians, including 19 children, on Monday.

The Syrian Observatory for Human Rights (SOHR) claims that Western air strikes on Raqqa have killed 167 civilians in the last eight days, marking a rapid rise in death toll than previously recorded. "The tolls are high because the airstrikes are hitting neighbourhoods in the city centre that are densely packed with civilians," said the director of SOHR, Rami Abdel Rahman.

"There are buildings full of civilians who are trying to get away from the frontlines."

Surge in death toll

The United States is carrying out the strikes in support of the Syrian Democratic Forces or SDF which in itself is a coalition of Kurdish and Arab militia.

The SDF have captured more than half of the city fighting against the so called Islamic State's militants.

There has been a surge in the civilian death toll in recent months because of US-led airstrikes. Airwars, a group that monitors air strikes in Syria and Iraq, estimates that at least 4,887 to 7,528 civilians have lost their lives as a direct result of Western airstrikes in the region since 2014.

But the US-led coalition, which also includes Britain, Australia and France, has assured that it considers every possible measure to avoid the killings of innocent people.

"We have opened up safe routes for civilians to cross securely towards areas controlled by our forces, who are rescuing civilians almost daily and transferring them to safe places," said Talal Sello, an SDF spokesman.

Civilians used as 'human shields'

It is believed that around 25,000 people are trapped inside Raqqa and the so called Islamic State is using them has 'human shields' to halt the assault from SDF soldiers. "One of the major reasons for the slow progress in the Raqqa fight is the preserving of civilian lives and avoiding massive losses among them," added Sello.

The airstrikes have been concentrated on the neighbourhoods in central Raqqa, and according to the human rights activists and citizen journalist group "Raqqa Is Being Slaughtered Silently" (RBSS), several families have lost multiple members of their household as a result.

The USA's Secretary of Defense Jim Mattis had visited the Iraqi capital of Baghdad on Monday and said that the so called Islamic State's "days are certainly numbered....But it's not over yet and it's not going to be over anytime soon," he swiftly added.

The coalition confirmed on Sunday that its jets had targeted an explosives cache, two machine gun units and two drone launching areas.