Enormous resources are being directed at trying to figure out who might be responsible for poisoning a former Russian spy and his daughter with a rare chemical agent.
Sergei Skripal, 66, and his daughter, Yulia, 33, were found unconscious on a bench in the southwestern English city of Salisbury on Monday.
Police and forensics officers today continued searching Skripal's home in Salisbury, located 145 kilometres southwest of London, as well as a pub and a restaurant he and his daughter were believed to have visited on Monday.
Skripal and his daughter are in critical but stable condition at a hospital in Salisbury.
A police officer who came to their aid is in a serious condition, though he is conscious and talking, Rudd said.
He was identified Thursday as Sgt. Nick Bailey.
"The use of a nerve agent on British soil is a brazen and reckless act," Rudd told lawmakers in the House of Commons.
"This was attempted murder in the most cruel and public way."
As speculation centered on suspicions that Russia was behind the attack, Rudd said "people are right to want to know who to hold to account.
But if we are to be rigorous in this investigation we must avoid speculation and allow the police to carry on their investigation."
Rudd said the "government will act without hesitation as the facts become clearer."
The Russian Embassy in London, which has mocked other British politicians for suggesting Russian involvement, tweeted that it agreed with Rudd: "First evidence then conclusions on Mr. Skripal's case. Responsible political approach."
Police have refused to speculate on who is behind the attack, but many have focused on Russia because of the case's similarity to the 2006 killing of another former Russian spy who was poisoned in London with radioactive polonium-210.