AMMAN: The US-backed forces currently battling the Islamic State in Raqqa city have shifted their strategy in the eastern districts, a commander told Syria Direct on Tuesday, slowing the pace of battle to reduce civilian casualties and the destruction of historic sites.

“The strategy has been changed,” a Syrian Democratic Forces (SDF) commander told Syria Direct from Raqqa city, "to save civilian lives." He asked not to be identified by name.

The commander said a reduction in the tempo of battles on the eastern front of Raqqa city was to prevent civilian casualties and preserve historic sites such as the Abbasid al-Atiq mosque in the heart of the walled Old City.

“We are fighting and advancing with great caution,” he said.

Concerns for civilians are likely not the only reason that fighting has slowed in Raqqa's Old City. There, "IS fortifications appear stronger," the commander said, and in two weeks of fighting, SDF forces have made only incremental advances.

In western Raqqa city, by comparison, US-backed forces reported the capture of two districts in the past 72 hours: al-Tayyar and Yarmouk.

The SDF—a multi-ethnic coalition of ground forces supported by United States-led coalition aircraft, artillery, weapons, advisers and ground forces—has been battling Islamic State fighters inside Raqqa city since June 6.

Currently in its sixth week, the campaign has resulted in the capture of roughly 35 percent of Raqqa city.

But each advance on the ground comes at a cost. In addition to reportedly rising casualties among the ranks of the SDF—though the force has not officially said how many—civilians trapped in the blockaded, urban area alongside Islamic State fighters are regularly coming under artillery fire and airstrikes.

Airwars, an independent monitor that tracks casualties and US-led coalition airstrikes in Syria and Iraq, published an investigation for the Daily Beast online Tuesday that found civilian casualties from coalition actions in Iraq and Syria have nearly doubled since the inauguration of American President Donald Trump in January.

The reported spike in civilian deaths—at least 2,200 this year alone, according to Airwars, while the US-led coalition cites a lower number of 603 killed total since 2014—comes after the Trump administration shifted tactics “from attrition...to annihilation,” as US Secretary of Defense James Mattis told CBS News in May.

The rise in civilian casualties also coincides with the most violent stages of the battles for Iraq’s Mosul and Syria’s Raqqa city, two densely populated, IS-held urban centers.

But while increased civilian casualties were not surprising as the offensive moved into Raqqa, the numbers so far have exceeded expectations, Chris Woods, the director of Airwars, told Syria Direct on Tuesday.

“In Syria, we’re talking about an almost exclusively US campaign,” said Woods. “And for months and months now we have seen far higher civilian fatalities that we just don’t think can be explained simply by the Raqqa offensive," referencing a possible change in US rules of engagement regarding civilian deaths, which the Trump administration denies.

“We remain concerned that both the SDF and the coalition do not appear to be prioritizing the protection of civilians during these heavy bombardments as much as they should,” Woods added.

Coalition munitions in Raqqa on July 17. Photo courtesy of Bulent Kilic/AFP.

On Tuesday, video and images from inside Raqqa city—some posted online by the Islamic State’s Amaq news agency—appear to show the use of white phosphorous in Raqqa city, as well as injured civilians.

White phosphorous, an incendiary weapon that is also used to obscure movements on the ground, has been used by US forces in both Mosul and Raqqa, Human Rights Watch reported in June.

The coalition admits using the munitions in Mosul, and pictures published by The Washington Post last month of US Marines deployed near Raqqa show the unit is equipped with artillery shells containing white phosphorous.

All artillery strikes in the Raqqa battles are currently being conducted by American coalition forces on the ground in and near the city, SDF sources told Syria Direct last month. Airwars’ Chris Woods gave a similar account.

“The majority of civilians killed in Raqqa are being killed by heavy weaponry, which is almost all from the coalition rather than from the SDF, as far as we can tell,” said Woods. “Often they cannot know whether civilians are present when they are conducting air and artillery strikes.”

While tens of thousands of civilians are still trapped in IS-held districts and prevented from leaving by active frontlines as well as Islamic State snipers and landmines, some have been able to escape Raqqa city.

On Monday, 525 people reportedly fled from western districts of Raqqa city and 75 people left the Old City, according to posts on official SDF social media accounts.

“We know that the SDF on the ground is doing everything it can to evacuate civilians from neighborhoods as it battles for them,” Woods told Syria Direct on Tuesday.

“We just think more care can and should be taken to protect civilians during these heavy bombardments.”