A US think tank has said that Russian forces could make further advances if the United States and European countries delay their military assistance to Ukraine.

The Institute for the Study of War provided its analysis on the situation in the key eastern city of Avdiivka.

It said, "Russian forces appear to have temporarily established limited and localized air superiority" and used a large amount of glide bombs "to provide close air support to advancing infantry troops."

The institute also said this is "likely the first time that Russian forces have done so in Ukraine."

It added that delays in Western security assistance "could allow Russian forces to replicate the close air support that facilitated Russian advances in Avdiivka at scale."

Russia's defense ministry announced on Saturday that its minister Sergei Shoigu told President Vladimir Putin that Avdiivka is under full Russian control.

Also on Saturday, Ukrainian President Volodymyr Zelenskyy gave a speech at an international conference in the German city of Munich.

He warned that keeping Ukraine in "an artificial shortage of weapons" allows Russia to adapt to the current intensity of the war.

Ukrainian Defense Minister Rustem Umerov said in a social media post that one of the lessons learned from the defense of Avdiivka is that Ukrainian forces need modern air defense systems.