RUSSIAN foreign minister Sergei Lavrov has said the country has "plenty of evidence" that Britain staged the chlorine gas attack in Douma, including chemicals he claims were made in Salisbury.

In an interview with the state-run Rossiya Segodnya news agency, posted on the Foreign Ministry website, Lavrov also alleged that videos showing people suffering the after-effects of the gas attack in the Syrian city were "staged by the White Helmets" rescue organisation.

He also accused the rescue organisation of terrorist links.

He added: "Also, just recently, our defence ministry's troops liberating Douma found a stockpile of chemicals produced in Germany, Porton Down and Salisbury, among others.

"Experts are now analysing the substances found there."

Russia's ambassador to London, Alexander Yakovenko, said they had "dozens" of proofs that the attack on Douma had been deliberately staged.

At a press conferences at the embassy in London, he showed Russian television footage which, he said, showed an 11-year-old Syrian boy who had appeared in a video of the incident in Douma issued by the White Helmets humanitarian group.

He said the boy, who was unhurt, had told Russian television that he had been called to hospital by the White Helmets where he had been offered "sweets and cookies" to appear in the video.

"The facts that have been presented by the Syrian government and Russia to show that the incident has been deliberately staged has been ignored," he said.

"We have dozens of these kinds of proofs. Everything that was done in Douma was staged."

Yakovenko said there was no justification in international law for the British, US, and French missile strikes on Syria which they mounted in response to the incident in Douma.

He said Theresa May's justification of "humanitarian intervention" had been widely rejected by the international community as a legal basis for military action.

"We have a legal justification that is based upon a non-existent rule of international law," he said.

"Under international law the military operation in Syria was blatantly unlawful."