The Russian Foreign Ministry on Thursday said that five of its citizens might have been killed in airstrikes the United States had carried out in the Syrian province of Deir ez-Zor on February 7, Reuters reported. The US had then claimed that it had killed 100 Syrian soldiers loyal to President Bashar al-Assad in self defence.

“Based on preliminary information, as a result of an armed encounter, the reasons for which are now being investigated, we could be talking about the deaths of five people,” the ministry’s spokesperson Maria Zakharova said. She added that the citizenship of those killed had not been verified, but clarified that they were not Russian military personnel.

The spokesperson for the US-led coalition battling the Islamic State group in Syria had said last week that efforts were made before and after the battle to avoid confrontation with Russian forces in the area that are supporting the Assad regime.

CBS News quoted unidentified American officials as saying that Russian mercenaries were present when the US missiles hit the forces fighting for Assad. Other media outlets too had reported that those killed were Russian mercenaries. The pro-Assad forces were most likely trying to capture oilfields in the region that had been liberated from the Islamic State group in September 2017, the coalition had said last week.