Dozens of Russian diplomats expelled from the US have landed in Moscow, amid warnings from Britain’s defence secretary  that the world is “entering a new era of warfare”.

Gavin Williamson said the poisoning of Russian former spy Sergei Skirpal and his daughter Yulia in Salisbury demonstrated the danger posed by Russia as the world becomes a “darker place”.

The poisoning early last month has sparked a number of tit-for-tat diplomatic expulsions, with the US and much of Europe standing behind the UK government’s accusations that Russia was behind the attack. The Kremlin has denied being involved and has promised to respond to all diplomatic measures in kind.

“If we were in any doubt of the danger posed by Moscow, we only have to look at events in Salisbury, where our Armed Forces… have been responding to a cold-blooded chemical attack,” according to Mr Williamson.

The minister also urged Britain to keep pace with the threat from the Kremlin in an article for the Sunday Telegraph to mark the centenary of the of the RAF.

“This was an illegal and contemptuous use of force against our country by the Russian State, endangering innocent lives,” he wrote.

“President Putin is using more hybrid capabilities to subvert, undermine, and influence countries around the world,” he added.

Mr Williamson, who has previously told Russia to “go away and shut up”, said the response of the Kremlin had been to “unleash a tidal wave of smears, lies and mockery”.

The UK expelled 23 Russian diplomats earlier this month. Russia retaliated by sending the same number of UK diplomats home from Moscow and on Saturday ordered Britain to cut just over 50 more of its staff.

On Sunday morning two planes carrying officials from the Russian embassy in Washington, the New York consulate and the United Nations landed at Vnukovo Airport outside Moscow. The US expelled 60 Russian diplomats.

Russia has demanded answers to a total of 41 questions about the Salisbury attack, including a request for information about the use of antidotes.

It has also accused Britain of “blatant provocation” after border force officers searched an Aeroflot plane at Heathrow.

The British government is considering a request to allow Russian officials to visit Yulia Skripal after it was reported her condition was rapidly improving.

Mr Skripal remains in a critical but stable condition in hospital while his daughter is said to be conscious and talking.