A 32-year-old traffic police officer caught red-handed during an attempted rape last week has admitted to carrying out a series of sexual assaults in southern Moscow and has been positively identified by 12 victims, investigators said.

The suspect, who is expected to be charged with multiple counts of rape and formally placed under arrest Monday, was arrested Thursday during a “planned operation,” Investigation Committee spokeswoman Marina Merkulova said Friday.

She refused to elaborate on the arrest or identify the suspect.

But police earlier said the suspect, identified in media reports as Lieutenant Artur Kositsyn, was detained in a sting operation as he tried to force himself on a woman in an apartment building elevator in southern Moscow.

Kositsyn worked for the Podolsk traffic police force in the Moscow region but was registered in an apartment in southern Moscow, where police had been searching for a serial rapist in connection with 20 sexual assaults since March, news reports said.

Kositsyn worked for the traffic police in southern Moscow until May, when he failed a mandatory annual psychological examination and was transferred by his superiors to a similar position in Podolsk, a town south of Moscow, reports said.

Kositsyn was fired from the Podolsk police force on Thursday, a Moscow region police spokesman told RIA-Novosti. He said the Moscow region's police chief had ordered an internal investigation into the regiment where Kositsyn had served.

Twelve of the 20 women believed to have been assaulted by the suspect have positively identified him as the attacker, Merkulova said. But there might be additional victims because women often do not report sexual assaults, she said.

Investigators in southern Moscow have set up a hotline at 8 (926) 821-8839 for information about other attacks that might be linked to the suspect.

Kositsyn, a heavily built man according to a photo published in Moskovsky Komsomolets, cruised around the neighborhood in an expensive Toyota Land Cruiser to hunt for victims while off-duty and used a knife to scare women into submission, investigators told the newspaper.

When he was detained, he offered police officers a bribe of 300,000 rubles ($10,000) to free him, and en route to the police station increased his offer to 1.5 million rubles ($50,000), Komsomolskaya Pravda reported.

Police set up the sting operation after being alerted by one of Kositsyn's targets, a 32-year- old woman who managed to escape him, news reports said.

Many local residents seemed to know little about the hunt for the serial rapist. Several told The Moscow Times on Friday that they had heard that the police were searching for a rapist who killed his victims. Kositsyn is not accused of killing any of his victims.