A wealthy Russian banker remains "critical but stable" under armed guard in hospital today after being gunned down in a suspected assassination attempt.
German Gorbuntsov is in a coma after he was shot several times as he entered his multimillion-pound executive apartment near Canary Wharf, east London.
Scotland Yard said it was "too early to speculate" on Russian reports that the attack could be a gangland hit linked to a murder attempt on another banker, Alexander Antonov, in Moscow.
The force's Trident command - which investigates gang shootings - is understood to have liaised with overseas counterparts in the hunt for the gunman behind the attack on Tuesday evening.
Police said the suspect, who is white, 6ft and slim, and was wearing dark clothes, was seen running away from Westferry Road after Mr Gorbuntsov was shot.
The man who attempted to murder Mr Gorbuntsov "was known" to his victim, according to his neighbour.
The 54-year-old management consultant was at home when the shooting took place.
He said: "I arrived home at 6.30pm and went upstairs, and around 9pm that night the police knocked on the door and mentioned there had been an incident, and that someone was critically injured and taken to hospital.
"They mentioned that the attacker was known to the person who'd been attacked.
"The morning after, I came down to go to work just before 7am and the glass here in the door was all smashed in.
"When the police mentioned the incident they hadn't said it was physically in the foyer," added the man, who gave his name only as John.
Tony Smith, 26, an estate agent, said he had been trying to drive down Byng Street moments after the shooting.
He said: "I pulled my car up and looked down and saw his body, saw him. Police were surrounding him but there were only two police cars, and the rest came later.
"The window was shot out on the door. I looked at him, I thought he had been stabbed at first. I didn't expect this to happen in this block."
Detectives said the shooting was not thought to be locally gang-related but a spokesman added: "This is sitting with Trident which investigates gang-related shootings. There is no reason it should rest with anyone else."
Mr Gorbuntsov's condition is described as critical but stable, a Met spokesman said today.
The victim, in his 40s, previously owned banks in Russia and Moldova, according to Russian media.
Police would not confirm Russian reports that the attacker had used a sub-machine gun and officers would not say where Mr Gorbuntsov is being treated.
A source said the victim was under armed guard and Trident officers are treating the incident as a gang-related crime after liaising with the force's counter-terrorism command.
Mr Gorbuntsov was shot as he entered the block of flats in Byng Street, where serviced apartments fetch up to £200 a day in rental income. Homes in the area are the choice of City highflyers, with easy links to Canary Wharf, the O2 Arena and London City Airport.
Russia's Kommersant newspaper quoted Mr Gorbuntsov's lawyer, Vadim Vedenin, who said his client had submitted evidence to police investigating the attack on Mr Antonov in 2009.
Three Chechen men were convicted of attempted murder in the case and given long jail sentences in 2010.
The apparent attempted assassination will prompt comparisons with the murder of Russian dissident Alexander Litvinenko in London in November 2006.
British prosecutors have named fellow ex-KGB agent Andrei Lugovoy as the main suspect in his poisoning with radioactive polonium-210, but the Russian authorities have repeatedly refused to send him to face trial in the UK.
Mr Litvinenko's widow, Marina, sent her thoughts to Mr Gorbuntsov's family.
"This must obviously be a very difficult time," she said. "I don't think it is very easy to say what has happened at this stage - they will be hoping for some clarity very soon."