A senior defense official said on Tuesday that the US cannot confirm the use of chemical agents in the Ukrainian city of Mariupol.

"We cannot confirm the reports that were out on social media yesterday that chemical agents were used in Mariupol ... We cannot confirm the use of chemical agents at this time. We're still evaluating," the official told reporters.

Ukrainian neo-Nazi Azov battalion claimed that chemical weapons have been used by Russian forces attacking the Ukrainian port of Mariupol.

However, no evidence of the use of chemical weapons has been presented.

On Its part, Russia has constantly warned against the use of chemical weapons by the Ukrainian neo-Nazi Azov battalion.

Nationalists also faced accusations from Moscow of holding hostages in a maternity hospital in Mariupol, which would not be the first crime committed by the notorious far-right neo-Nazi group, as they opened fire on civilians during their evacuation from the city, killing at least two people and injuring four others.

On its part, the European Union said that it is "closely monitoring" allegations made by Ukrainian nationalists that the Russian military used chemical weapons against Ukrainian soldiers in Mariupol, according to Nabila Massrali, Spokesperson for the EU Commission's Foreign Affairs and Security Policy.

"We have seen the press report about the alleged use of the chemical substances by the Russian armed forces in Mariupol after the Ukrainian soldiers presented signs of chemical poisoning. We are of course following the situation closely," Massrali added.

The United States, the European Union, and the United Kingdom have all stated that they are working to learn more about the alleged use of chemical weapons in Mariupol.