U.S. distances itself from pro-Ukraine incursion into Russia that involved American military vehicles

The United States has sought to distance itself from a dramatic raid into Russian territory by pro-Ukraine fighters who appeared to use American equipment in their attack.

Moscow said Tuesday it had fought off an assault in its Belgorod region after two days of battles with attackers who had staged a cross-border raid.

Much is unclear about the fighting. Russia says the raid was conducted by saboteurs from the Ukrainian military; Ukraine says it was carried out by Russian citizens who rose up independently.

Washington has provided billions of dollars of military assistance to Kyiv, but has sought to restrict its use to the defense of Ukrainian territory, rather than attacks on Russian soil that could potentially be used as a reason for the Kremlin to escalate the conflict.

Video posted by the Russian Defense Ministry and verified by NBC News show American-made Humvees and MRAP armored vehicles at a Russian border checkpoint following the alleged incursion by pro-Ukraine and anti-Putin fighters.