A pileup of about 10 cars on Bolshoi Krasnokholmsky Bridge snarled traffic along the Garden Ring Road on Wednesday afternoon, Interfax reported.
Details were sketchy, and it was not immediately clear whether anyone had been injured in the accident. But Interfax, citing a reporter at the scene, said no one had died.
The report also said debris from the crash was scattered into the opposite lane of traffic.
Traffic police were investigating at the scene.
The Bolshoi Krasnokholmsky Bridge, which is part of the Garden Ring, stretches between Taganksaya Ploshchad and Nizhnaya Krasnokholmakaya Ulitsa. The bridge was built in 1938 and, at 168 meters, is the longest in downtown Moscow.