Top UN official on genocide prevention expressed fears Wednesday that the battle to take Raqqa from ISIS is wreaking havoc on civilians.

Axar.az reports citing AA that, “I am deeply disturbed by reports coming out of Raqqa of the horrendous situation faced by civilians caught up in the offensive to retake the city from the so-called Islamic State of Iraq and the Levant (ISIL)," Adama Dieng said, referring to the ISIS terrorist group.

He said the Syrian city, where 25,000 civilians remain trapped, was under heavy bombardment by the U.S.-led anti-ISIS coalition.

The impact on civilians is exacerbated by the fact that ISIS militants use them as human shields and kill those who try to flee while the Syrian regime continues its "indiscriminate" attacks, Dieng said.

"The legitimate aim of retaking Raqqa must not be achieved at such a high cost to civilians," he said, urging international actors to take necessary measures.

In June, the U.S.-led anti-ISIS coalition -- along with the terrorist PKK/PYD group -- launched a campaign aimed at retaking Raqqa, the capital of ISIS's self-proclaimed “caliphate.”

Some 450,000 civilians were later forced to leave their homes in Raqqa, while 30,000 others were caught in the middle of intense coalition bombardments.

According to the monitor group, Raqqa Is Being Slaughtered Silently, at least 481 civilians were killed in the city in the month of July alone.

Last month, the Syrian Network for Human Rights, a U.K.-based rights watchdog, documented the deaths of some 1,400 civilians in Raqqa -- including women and children -- since the beginning of the year.

Syria has been locked in a vicious civil war since early 2011, when the regime of Bashar Al-Assad cracked down on pro-democracy protests with unexpected ferocity.

Since then, hundreds of thousands of people have been killed and more than 10 million displaced, according to the UN, although Assad regime officials put the death toll much lower.