Britain will methodically work out who carried out a nerve agent attack on a Russian ex-spy and his daughter, then take robust action, interior minister Amber Rudd said yesterday.
Former double agent Sergei Skripal, 66, and his daughter Yulia, 33, have been in hospital since they were found unconscious on Sunday on a bench outside a shopping centre in the southern English city of Salisbury.
"Both remain unconscious, and in a critical but stable condition," Home Secretary Rudd told parliament.
British media and some politicians have speculated that the Russian state could be behind the attack - suggestions dismissed by Moscow as knee-jerk, anti-Russian propaganda.
"The use of a nerve agent on UK soil is a brazen and reckless act. This was attempted murder in the most cruel and public way," Rudd said. But she urged not to speculate on the subject.
"We will respond in a robust and appropriate manner once we ascertain who was responsible," she said. "We are committed to do all we can to bring the perpetrators to justice, whoever they are and wherever they may be."
Police said on Wednesday that a nerve agent was used against Skripal and Yulia. A police officer who was also harmed by the substance was now able to talk to people.
Scientific tests by government experts have identified the specific nerve agent used, which will help identify the source, but authorities have refused to disclose the details.
Skripal betrayed dozens of Russian agents to British intelligence before his arrest by Russian authorities in 2004. He was sentenced to 13 years in prison in 2006, and in 2010 was given refuge in Britain after being exchanged for Russian spies.
The attack on him has been likened in Britain to the assassination of ex-KGB agent Alexander Litvinenko, a critic of Putin, who died in London in 2006 after drinking green tea laced with radioactive polonium-210.