British detectives were scrambling Thursday to uncover who poisoned a Russian former double-agent and his daughter with a nerve agent, as doctors battled to save their lives, in a case that threatens to further damage Londons ties with Moscow. Sergei Skripal, 66, who moved to Britain in a 2010 spy swap, is in a critical condition in hospital along with his daughter Yulia after they collapsed on a bench outside a shopping center in the southwestern English city of Salisbury on Sunday. On Wednesday, British police confirmed for the first time that a nerve agent was used and that their probe was now an attempted murder investigation. Scientific tests by government experts have identified the specific nerve agent used "which will help identify the source", Metropolitan Police assistant commissioner Mark Rowley told reporters. Police say they are keeping an open mind about what happened, but Foreign Secretary Boris Johnson has alluded to Russia. He noted the "echoes" with the 2006 poisoning in London of former Russian spy and Kremlin critic Alexander Litvinenko, which Britain has blamed on Russia. Moscow accused British politicians and journalists of whipping up anti-Russian sentiment, with Kremlin foreign ministry spokeswoman Maria Zakharova telling reporters the story "was straight away used to boost an anti-Russian campaign in the media". Zakharova earlier said Johnsons comments were "wild". Meanwhile, hundreds of counter-terrorism detectives are working "around the clock" to create a timeline of the victims movements, with "many hours" of CCTV under review, police said. Investigators believe Skripal and his 33-year-old daughter were in Salisbury city center for several hours before they were found slumped on a bench. They reportedly had lunch at a pizza restaurant, Zizzi, and visited a pub in Salisbury before being discovered outside the shopping center, where onlookers said they appeared "out of it". An anonymous witness who was in the pub, which has been closed by police, told the BBC on Wednesday that Skripal was there behaving erratically and at one point shouting loudly. Rowley appealed for information from those in Salisbury on Sunday. A policeman is also ill after coming to the aid of Skripal and his daughter. British media reports suggest the three victims are seriously ill.  Britains Sky News, quoting sources, said all three victims are in a coma. The Times newspaper, quoting a senior unnamed British government official, said Skripals condition was thought to be particularly severe. Skripal was a former colonel in Russian military intelligence who was jailed in his country for betraying agents to Britains MI6 secret service. He was pardoned before being flown to Britain as part of a high-profile spy swap involving Russia and the United States in 2010.