Armenian and Azerbaijani delegations have scuffled in Moscow during a commemoration of World War II veterans after an argument erupted over the breakaway Nagorno-Karabakh region.

The incident unfolded in central Moscow during a government-organized procession called the Immortal Regiment, in which people march bearing photographs of loved ones who died in the war or survived it.

The fight broke out as members of an Armenian delegation waved flags of Nagorno-Karabakh, a mountainous region held for more than two decades by Yerevan-backed separatists within Azerbaijan's internationally recognized borders.

Shouting and shoving between the two sides ensued, as chants of "Karabakh" emerged from the crowd, a video of the incident showed. Unidentified men also hurled objects, while one man can be seen trying to smash a pair of sticks attached to Azerbaijani flags.

Police intervened, though it was not immediately clear if anyone was detained in the altercation.

Armenia-backed separatists seized control of the mainly ethnic Armenian Nagorno-Karabakh during a war in the early 1990s that killed some 30,000 people. Diplomatic efforts to settle the conflict have brought little progress.

Sporadic Armenian-Azerbaijani clashes have become particularly frequent in recent years. Four days of heavy fighting in April 2016 reportedly killed dozens on both sides.

Victory Day, the annual May 9 celebration of the defeat of Nazi Germany, is one of the most revered and solemn holidays across the former Soviet Union.

Pro-Armenian and pro-Azerbaijani websites on May 9 each accused the other side of provoking the scuffle.

Armenian President Serzh Sarkisian marked Victory Day this year in Nagorno-Karabakh, attending a military parade in the regional capital, Stepanakert.

With reporting by RFE/RL's Russian Service and Dozhd