Russia's foreign minister has said Moscow could help Britain investigate the poisoning in Salisbury of an ex-Russian spy, but expressed resentment of suspicions cast on his country.
Sergei Lavrov's comments in the Ethiopian capital Addis Ababa came as British investigators scrambled to unravel the nerve-agent poisoning of Sergei Skripal and his daughter.
Mr Skripal, a former Russian military intelligence officer, was convicted in 2006 of spying for Britain and released in 2010.
Mr Lavrov added: "But in order to conduct such cases, it is necessary not to immediately run out on TV screens with unfounded allegations."
British Home Secretary Amber Rudd arrived at the scene in Salisbury today where where she talked with Wiltshire Police temporary chief constable Kier Pritchard, the local Conservative MP John Glen and business owners.
Ms Rudd did not reveal any further details about the substance, how it was deployed, or who used it.
Visiting Salisbury, she said: "I understand people's curiosity about all those questions, wanting to have answers and there will be a time to have those answers.
"But the best way to get to them is to give the police the space they need to really go through the area carefully, to do their investigation and to make sure that they have all the support that they need."
Ms Rudd added: "At the moment our priority is going to be the incident, which is why I'm here in Salisbury today, making sure that everybody's protected around the incident, making sure the emergency services have had the support that they need and will continue to get it.
"In terms of further options, that will have to wait until we're absolutely clear what the consequences could be and what the actual source of this nerve agent has been."
Asked about the condition of Mr Skripal, his daughter and DS Nick Bailey, Ms Rudd said: "Still very serious for the two people who were indeed the subject of this outrageous attack and for the police officer, I understand it's still serious, although he's still conversing and engaging."
Simon Kempton, the Police Federation's operational policing lead, paid tribute to Detective Sergeant Nick Bailey, the police officer critically injured responding to the Salisbury nerve agent attack.
"He's really highly regarded. Everyone knows Nick and he's really well thought of," he said.
Speaking at the police cordon, yards away from the bench where Skripal and his daughter were found, Mr Kempton said: "He's receiving the best possible medical care. The NHS is doing an amazing job.
"He's in a very serious condition. I haven't been to see him, but my colleagues and his Chief Constable have. He's sitting up and talking, but his condition is very serious.
"He's obviously being treated for the effects of nerve agent contamination."