The UK has been encouraged by the “strength of support” from allies to take action against Russia after the nerve agent attack on a former spy and his daughter, Boris Johnson said just hours before the US secretary of state, Rex Tillerson, was sacked by Donald Trump.
Tillerson, who spoke to the foreign secretary on Monday afternoon, had told reporters the attack on Sergei and Yulia Skripal “clearly came from Russia” and would have consequences.
His remarks went further than those of Theresa May, who told the House of Commons on Monday it was “highly likely” Russia was behind the attack. The White House press secretary, Sarah Huckabee Sanders, had stopped short of pointing the finger at Russia.
Just hours after Johnson had welcomed US support, Trump tweeted that he had replaced Tillerson with the CIA director, Mike Pompeo. The sacking may not be linked to Tillerson’s comments on Russia; relations between the pair are believed to have been deteriorating for some time, especially over the Iran nuclear deal and Trump’s announcement that he would meet the North Korean leader, Kim Jong-un.
It is unclear when Tillerson learned that his dismissal was imminent. It was first reported he had known since Friday, which was denied by sources, and a state department spokesman later said Tillerson “did not speak to the president and is unaware of the reason” and later suggested he had read the news on Twitter.
The US president said he would speak to the British prime minister about the Salisbury poisoning on Tuesday.
Trump said: “It sounds to me like they believe it was Russia … I would certainly take that finding as fact.” But he added: “If we get the facts straight we will condemn Russia, or whoever it might be.”
Downing Street is hoping for a strong statement of support from Trump when he speaks with May on Tuesday, having previously been encouraged by such direct condemnation from Tillerson.
Skripal and his daughter remain in hospital in a critical condition while the Wiltshire police detective sergeant Nick Bailey is in a serious but stable condition.
Bailey is making good progress, Britain’s most senior counter-terrorism police officer said. Delivering an update on the police investigation outside New Scotland Yard on Tuesday, the Metropolitan police deputy assistant commissioner, Neil Basu, said 38 people were seen by medical staff in the aftermath of the “reckless, despicable and targeted” attack.
Of those, 34 have been assessed and discharged and one more person is still being monitored as an outpatient but is not showing signs of illness. Previously, police had said 21 people had been affected.
In an interview earlier on Tuesday, Johnson repeated May’s ultimatum to the Kremlin that it must explain by midnight on Tuesday if it was behind the attack, or if it had allowed the deadly nerve agent novichok to get into the wrong hands.
“If they can come up with a convincing explanation, then obviously we will want to see full disclosure of that to the Organisation for the Prohibition of Chemical Weapons in The Hague,” Johnson said.
The Russian foreign minister, Sergei Lavrov, said Russia had requested access to the substance to perform its own checks but the request had been refused. May’s spokesman hit back at Lavrov’s suggestion that Britain could be violating the chemical weapons convention.
“The UK fully complies with all of its obligations under the chemical weapons convention,” the spokesman said. “Under the chemical weapons convention, states have the mechanism to consult but there is no requirement to do so.”
May updated her cabinet on the unfolding investigation into the Salisbury attack, telling ministers there was “no doubt of the severity” of what had taken place.
Should Russia give no credible explanation, the UK is likely to expel a number of diplomats, more than the four who were told to leave the UK after the death of the former Russian security agent Alexander Litvinenko. The UK may also mount a covert cyber-offensive against the Kremlin.
Any direct action may be covered under article 51 of the UN charter, which allows legitimate self-defence, but Downing Street denied May was trying to win support to invoke article 5 of the Nato treaty on common defence.
The measures, which the Foreign Office has previously resisted, saying it already has the full confiscatory powers it needs, are highly symbolic, having been already adopted by the US, but ministers are likely to support a specific “Magnitsky clause” in the bill at report stage.
Ministers may also consider whether to direct the broadcasting regulator, Ofcom, to investigate whether Russian media outlets, such as RT, are fit to hold broadcasting licences and whether senior officials could be told to boycott the football World Cup in Russia this summer.
Russia has denied being behind the attack on Skripal, a former double agent who came to the UK in a spy swap in 2010, and his daughter.
During an election campaign trip, the Russian president, Vladimir Putin, dismissed questions about the Skripals when confronted by the BBC, saying: “Get to the bottom of things there, then we’ll discuss this.”
The UK’s national security council was expected to meet on Wednesday to discuss the Russian response before the prime minister updates MPs. The home secretary, Amber Rudd, chaired a meeting of the government’s Cobra emergency committee in Whitehall on Tuesday morning to discuss the latest developments.