Mr Skripal's house and his auto have also been cordoned off.
The British government deployed the military Friday to help with its probe of the mysterious nerve-agent poisoning of a former Russian spy and his daughter - an apparent assassination attempt that also left 19 others seeking medical treatment.
But he warned: "He is not the Nick that I know. he is very anxious, he's very concerned".
Police said troops were being called in because "they have the necessary capability and expertise" and health advice remains the same - there is no broader risk to the public.
National counter-terrorism police, who are leading the investigation, announced on Friday that they had requested assistance from the military "to remove a number of vehicles and objects from the scene". They are in critical condition in a local hospital.
The Ministry of Defence regularly assists the emergency services and local authorities in Britain.
Police extended the cordon around the modest suburban home of Sergei Skripal in Salisbury, the quiet city in southwestern England where he and his daughter Yulia were found slumped on a bench on Sunday. The pair are critically ill after being attacked with an undisclosed nerve agent.
"This being treated as a major incident involving attempted murder by administration of a nerve agent", Rowley said but did not specifically mention the nerve agent.
Mr Lavrov has been quoted as saying by state news agency Tass that "whether it's poisoning of some British subjects, whether it's rumours about interference in the U.S. election campaign, if assistance really is needed, then we are ready to consider its possibility".
Lavrov added: "But in order to conduct such cases, it is necessary not to immediately run out on TV screens with unfounded allegations".
'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'.
He was sentenced to 13 years in prison in 2006, and in 2010 was given refuge in Britain after being exchanged for Russian spies.
Meanwhile, Russia's foreign minister expressed resentment at suggestions Moscow was behind the attack and said the Kremlin was "ready to consider" lending a hand in any investigation, "whether it's [about] poisoning of some British subjects, whether it's rumors about interference in the USA election campaign".
Britain's Home Secretary Amber Rudd (right) visited Salisbury on Friday..
Mr Skripal, an ex-Russian military security colonel, and his daughter remain in a critical condition at Salisbury District Hospital.
"Of course, if action needs to be taken, then the government will do that".
In a flagrant contradiction with the claims of United Kingdom police, Russian Federation has asserted that the spy, Sergei Skripal, now under treatment at a Salisbury hospital, was actually a British spy instead of Russian Federation.
British authorities say it's too soon to lay blame, but suspicions have fallen on Russian Federation.