An anti-extortion operation in Moscow has ended in the deaths of two police officers after the suspects opened fire, Russian media report.
Police attempted to arrest three suspects outside a building on the Leningrad Road, one of the city's most important transport arteries.
All three were arrested but two officers were mortally wounded.
Separately, two police officers were shot and wounded while investigating a robbery in the city centre.
In that incident, on Komsomol Avenue in the city centre, one of the suspects was shot dead, two others were injured and the fourth was arrested unhurt.
Gun crime remains a serious threat in Moscow though the homicide rate has fallen sharply since the post-Soviet chaos of the 1990s, when it reached a peak and shootings were a common occurrence in the Russian capital.
According to Life News, a Russian news website which specialises in crime stories, the two dead policemen were both respected captains in the northern Moscow crime squad, with long experience of police work.
The shooting erupted outside a branch of McDonalds on Thursday afternoon, when the police attempted to arrest the suspects, all of whom were wanted on suspicion of extortion, the website says.
The second shooting occurred around midnight when police were alerted to an apparent robbery in progress in a flat.
One of those arrested is an alleged Georgian career criminal, Rezo Bukhnikashvili, nicknamed Petso.
Mr Bukhnikashvili was also arrested in March of this year. No details of when or why he had been released were immediately available.