British diplomats will confront Russia later as the United Nations Security Council discusses the Salisbury novichok attack.
Britain has called the meeting to update council members on the investigation into the attempted murder of former spy Sergei Skripal, his daughter Yulia and police officer Nick Bailey.
It comes a day after two men suspected of being Russian spies were named as the prime suspects in the Salisbury attack.
Prime Minster Theresa May said Alexander Petrov and Ruslan Boshirov were Russian intelligence officers and the attack had been approved “at a senior level of the Russian state”.
But a spokeswoman for the Russian foreign ministry said the names of the men and their photos “say nothing to us”.
The Kremlin has denied any role in the poisoning of the Skirpals, who were found slumped on a park bench after being exposed to the military nerve agent on 4 March.
Speaking in the House of Commons, Mrs May said based on “a body of intelligence” the government had concluded suspects Petrov and Boshirov were officers from the Russian intelligence agency GRU.
“The GRU is a highly disciplined organisation with a well-established chain of command,” she said.
“So this was not a rogue operation… It was almost certainly also approved outside the GRU at a senior level of the Russian state.”
She told MPs that the UK would push for new sanctions against Russians responsible for cyberattacks and additional listings under the existing regime.
She also promised to work with the UK’s intelligence allies to “counter the threat posed by the GRU”.
The two suspects, who are both believed to be around 40, are likely to have been travelling under aliases, police said.
Detectives believe the novichok was smuggled into the UK in a fake, specially adapted Nina Ricci perfume bottle before it was applied to the front door of Mr Skripal’s house.
CCTV images showed the movements of Petrov and Boshirov after they arrived into Gatwick Airport on a flight from Russia on 2 March.
The men stayed at a hotel in east London before travelling to Salisbury on 3 March for a “reconnaissance” of the area, the Metropolitan Police said.
The suspects returned to Salisbury a day later and were spotted near Mr Skripal’s house.
They boarded a flight from Heathrow Airport to Moscow that evening.
Police revealed tests showed traces of novichok in the room at the City Stay Hotel in Bow Road, east London, where Petrov and Boshirov had stayed.
England’s chief medical officer said anyone who stayed at the hotel between 4 March and 4 May should contact the investigation team.
A spokesman for the hotel said it was “open for business as usual” and had been “fully supporting the police investigation”.
The Crown Prosecution Service (CPS) said there was “sufficient evidence” to charge Petrov and Boshirov with the attempted murder of Mr Skirpal, his daughter Yulia and Mr Bailey.
The suspects also face charges of conspiracy to murder Mr Skripal, the use and possession of novichok contrary to the Chemical Weapons Act, and causing grievous bodily harm with intent to Ms Skripal and Mr Bailey.
A European arrest warrant has been obtained but the CPS said it will not be applying to Russia for extradition, as the country does not extradite its own nationals.
Met Police assistant commissioner Neil Basu said officers had linked the Salisbury attack to the incident four months later in nearby Amesbury, which saw Dawn Sturgess, 44, and Charlie Rowley, 45, poisoned.
Ms Sturgess died on 8 July, days after she was taken to hospital. She was exposed to the same nerve agent used on the Skripals in Salisbury.
“We do not believe Dawn and Charlie were deliberately targeted, but became victims as a result of the recklessness in which such a toxic nerve agent was disposed of,” Mr Basu said.
The UK summoned a Russian diplomat in London on Wednesday to stress that those responsible for the poisoning must be brought to justice, the PM’s spokesman said.