Moscow was at the centre of the investigation into the poisoning of Alexander Litvinenko tonight after a radiation alert on several aircraft that flew to the Russian capital.
Friends of the former spy said the discovery of radioactivity on at least two British Airways planes further reinforced claims that Russia's security agents were behind the poisoning.
But there was another dramatic twist in the saga tonight with fresh poisoning claims involving the former Russian Prime Minister Yegor Gaidar.
Mr Gaidar is gravely ill and until recently was receiving treatment in Ireland - where he had been attending a conference - for what was thought to have been a diabetes-related condition.
He has since returned to Moscow, but tonight one of Mr Gaidar's aides said the doctors treating him there now believed he too had been poisoned.
"Doctors don't see a natural reason for the poisoning and they have not been able to detect any natural substance known to them in Mr Gaidar's body," spokesman Valery Natarov said. "So obviously we're talking about poisoning (and) it was not natural poisoning."
Officially, Scotland Yard made no comment on the Gaidar revelations. Detectives are aware of the case, but have had no involvement so far, while Alex Goldfarb, one of Mr Litvinenko's closest friends, said it was too early to draw any links between the two.
The Litvinenko investigation meanwhile, continued to gather pace today.
:: The inquest into his death was opened and adjourned at St Pancras coroner's court in north London where Dr Andrew Reid confirmed it appeared as though he had been exposed to, or administered polonium 210.
:: Home Secretary John Reid revealed that the number of contaminated sites had doubled from six to 12 and was likely to rise again.
:: Mr Reid also revealed that another two aircraft had been caught up in the radiation alert, although one was later given a clean bill of health. Government scientists are still pursuing a Russian aircraft to search for traces of alpha radiation - the type emitted by polonium 210.
:: Metropolitan Police Commissioner Sir Ian Blair said the cost of the police investigation so far was £300,000.
But tonight it was the Moscow connection in the spotlight, after it emerged three grounded planes flew between London and the Russian capital more often than any other route.
An initial sweep by Home Office scientists found low levels of radioactive traces on two of the aircraft, Boeing 767s, at Heathrow. A third is grounded in Moscow.
At the opening of the inquest into Mr Litvinenko's death today, Mr Goldfarb said: "If you look at the flight numbers BA have released, the first flight they are interested in was five days before the poisoning - the Moscow-Heathrow flight on October 25.
"This tells you that the police are looking for the ways of delivery of this material into London and this reinforces the theory that the origin of this material that killed Alexander was in Moscow.
"We still believe this is a murder perpetrated by agents of Russia's intelligence services."
There have been no arrests in the investigation so far. Mr Litvinenko's death is still being treated as suspicious.
Ex-KGB man Mr Litvinenko, a fierce critic of Russian President Vladimir Putin, died on Thursday last week. In his deathbed statement he accused Putin of being behind his poisoning. The Kremlin has denied any responsibility.
Among the 12 locations where traces of contamination have been discovered are the Itsu sushi restaurant in Piccadilly, the Millennium Hotel in Grosvenor Square, Mr Litvinenko's home, a friend's car apparently used to take him to hospital, Barnet General Hospital, University College Hospital, and the two grounded BA aircraft at Heathrow.
BA estimates that 33,000 passengers and 3,000 staff are involved in the alert relating to their grounded aircraft. A total of 221 flights to 10 destinations from October 25 to November 29 are being examined.
However, the Health Protection Agency (HPA) insists the health risk to the passengers is likely to be extremely low.
So far NHS Direct has received 1,707 calls since the radiation scare began. Call levels were five times higher than usual following last night's alert.
BA said there had been 5,500 calls to the company's hotline and 60,000 hits on the part of its website dealing specifically with the radiation alert.
A post-mortem examination will be carried out at the Royal London Hospital tomorrow, with special precautions being taken because of the nature of Mr Litvinenko's death.