The UK's Foreign Minister Boris Johnson has said London would submit a sample of the Novichok nerve agent used in former Russian spy's poisoning to the Organisation for the Prohibition of Chemical Weapons (OPCW), a UN body.

Speaking to the BBC news on Thursday, Johnson said the rare Soviet-made chemical weapon used against Sergei Skripal and his daughter Yulia in the British town of Salisbury was specifically chosen to send a message to political dissenters challenging Russia's President Vladimir Putin.

"There is a reason for choosing Novichok. In its blatant Russian-ness, the nerve agent sends a signal to all who may be thinking of dissent in the intensifying repression of Putin's Russia," he said.

"The message is clear: We will find you, we will catch you, we will kill you - and though we will deny it with lip-curling scorn, the world will know beyond doubt that Russia did it."

The attack showed the Kremlin was "clearly willing to act without restraint" and fit a pattern of "reckless behaviour" by Putin, Johnson said.

He also said that only Russia had the means and motive for carrying out the attack on Skripal.

Later on Thursday, Maria Zakharova, the Russian foreign ministry spokeswoman, described the British allegations as "insane" and accused the country of "Russophobia" as well as hiding "the truth" about the Skripal case.

Speaking at a routine press conference, Zakharova told reporters she wanted to comment on "the statements made by the prime minister of Britain [Theresa May] in parliament with completely insane accusations towards the Russian Federation, our entire country, our entire people".

"In connection with the introduction by Britain of unfriendly steps towards Russia, we plan to introduce reciprocal steps, without doubt... They are currently being worked on and will be adopted in the near future," she said.

She accused Britain of refusing to cooperate with Moscow on the investigation into the incident.

"We are extremely concerned by what happened a few days ago on British territory, we view with great concern all information we are receiving about the use of chemical weapons on British territory," Zakharova told the briefing.

"Britain is refusing to provide any factual information on this case. There is no mention about, for example, providing Russia with samples of the substance that was found at the crime scene," she said.

"I can confirm again, Britain has not provided to Russia any information, any details that might shed some light on the situation."

Zakharova said she wondered how other countries could show support for the UK in the Skripal case if they did not possess information about the case, referring to the White House statement that said Washington stood in solidarity with London.

After her remarks, France also said it agreed with the UK that Russia was behind the Skripal attack.

"Since the beginning of the week, the United Kingdom has kept France closely informed of the evidence gathered by British investigators and evidence of Russia's responsibility in the attack," the office of President Emmanuel Macron said after a telephone call between Macron and May.

"France agrees with the United Kingdom that there is no other plausible explanation and reiterates its solidarity with its ally."

Skripal, 66, and his daughter Yulia, 33, were found unconscious on a bench outside a shopping centre in Salisbury on March 4, after they were poisoned. The two remain in critical condition in a hospital.

A former double agent, Skripal betrayed dozens of Russian agents to British intelligence before his arrest in Moscow in 2004. He was later sent to the UK in exchange for captured Russian spies.

London ordered the expulsion of 23 Russian diplomats over the murder attempt and said that cabinet ministers and members of the royal family would not attend the World Cup in Russia this summer.