Moscow, Russia | Russian police said they were probing a cheeky stunt by a group of passengers on the Moscow metro who stripped down to their underwear as part of a worldwide flashmob. 

Police failed to see the funny side after the group rode the Moscow metro wearing warm coats with their boxer shorts or briefs and posted images online as part of the so-called "No Pants Subway Ride" event that originated in the United States.

"The police force on the Moscow metro are carrying out a check into the holding of the 'flashmob' in the metro," a Moscow police spokesman told RIA Novosti news agency.

"A decision is being taken on whether their actions constitute an administrative offence."

A spokesman for the police force in the Moscow metro told AFP however that even if the participants had been detained, it was unlikely they had committed even a public order offence.

The Moscow metro responded with a statement calling for passengers to "treat each other with respect and observe the generally accepted rules of behaviour in public places."

It was the first time Russians had taken part in the jokey flashmob which originated in New York in 2002 but has now spread to cities including London and Bangkok. 

The idea is that participants behave exactly like normal commuters, just without skirts or trousers.

One of the at least half-dozen Moscow participants, Mark Vesely, wrote on VK social networking page  afternoon that "the first official No Pants in the Subway flashmob was a success."

He posted photographs of a handful of bare-legged participants sitting in down jackets and underwear in a metro carriage.

The flashmob started from the central Tverskaya metro station, Vesely wrote.

Vesely complained, however, that not all had gone to plan, with one couple simulating sex during the flashmob, which he said was "unacceptable."

A splinter group from Russia's main Communist Party, the Communists of Russia, on Monday angrily denounced the stunt as "shameless and amoral" and called for the participants to be "charged with a crime for hooliganism in a public place."

Snow fell on Moscow  and daytime temperatures were around minus 13 degrees celsius (8.6 Fahrenheit), although inside the metro system is considerably warmer.

Moscow police have little tolerance for youth culture stunts and in 2011 detained costumed participants in a "zombie parade" down a pedestrian street.