SALISBURY Novichok victim Sergei Skripal was targeted for assassination because he was still an active spy for four Western intelligence agencies - including Britain's MI6, it has been claimed.

The 67-year-old supposedly retired Russian double-agent had betrayed Moscow in Spain, the Czech Republic and Estonia since moving to the Wiltshire town eight years ago.

The final straw for the Kremlin came when he fingered four spooks - including an old colleague - on undercover operations in the Baltic state of Estonia in 2016 and last year.

Revenge-hungry Moscow then sent-in two GRU military intelligence agents disguised as tourists Ruslan Boshirov and Alexander Petrov for the bungled nerve agent hit on Skripal.

The claims have been made in Germany's respected Focus magazine which quotes a "senior employee of NATO counter-espionage Allied Command Counterintelligence (ACCI)" from its headquarters in Brussels, Belgium.

The mag's article supports broad speculation since the failed hit in March that Skripal was still immersed in the murky world of espionage with his work channelled through an MI6 handler.

Chief reporter Josef Huffelschuelte, an acclaimed military and intelligence writer, said Skripal was deployed to Prague in 2012, two years after he was pardoned by Moscow and traded on a spy exchange with the UK.

With British assistance, the ex-colonel was expected to inform "local security authorities about active espionage networks of the Russians".

The NATO source stated Skripal's information was "so precise", Czech officials afterwards travelled several times to Salisbury to debrief him.

Skripal then served on the Costa del Sol for Spain's CNI secret service feeding information on Russian gangs hand-in-hand with oligarchs and high-ranking officials and politicians in Moscow.

The double-dealer had previous experience in the Iberian country - setting up a Spanish wine export business with a shady business partner in 1995 as he passed secrets of 300 colleagues to The West.

In July 2016, Focus reports, Skripal travelled to Tallin in nervous Estonia, which shares a 180-mile frontier with Russia and teems with its spooks.

It fears a Crimea-style takeover by hardline leader Vladimir Putin amid continuing border exercises by the president's army countered by a rival NATO build-up.

The Berlin-based magazine says: "Skripal, a man of good memory, identified at least three agents including an Estonian army officer and his father who he knew from their time in Moscow.

"The arrest of another spy (in Estonia) in January 2017 is linked directly to him."

The NATO source concludes in the mag: "Is it not highly comprehensible that the Russians wanted to punish this treachery?"

Skripal was thought to be still an agent as he fought for life alongside poisoned daughter Yulia, 33, on a visit to see her father.

He had spoken of "business meetings" in Poland, and met once a month with a "well spoken Englishman in a tweed suit" at the Cote Brasserie in Salisbury.

The 'tweed man' is believed to have been his MI6 'handler' - who cannot be identified for his own safety - but who allegedly did work with a UK security consultancy behind a dossier on US President Donald Trump's dealings with Russia.

Cote waitress Dagmara Wieczorak, 34, said at the time: “They always sat in the same seat, at the far end of the restaurant by the window looking out over the water.

“Sergei was very charming, always dressed in a smart shirt, while the Englishman was very well-spoken, very polite.

“They changed between Russian and English. I overheard them talking about travel. They seemed to be going back and forth to Warsaw all the time – they were moaning about the price of tickets."

Brasserie supervisor Matt McKenna added: “They would come in during the afternoon, they’d never book.

“It was random when they’d arrive, any day of the week, but at least once a month. They spent well, it was always well over £100."

Weronika Paliszewska, 35, owner of Taste The World Polish delicatessen in Salisbury where Skripal was a regular, said: "He would come here at least once a month. He visited Poland a lot, he used to tell me.

"He talked about traveling a lot. He's been back to Russia once in the past couple of years.”

This week supposed sports nutrition expert Boshirov - one of the 'tourists' whose weekend trip to Salisbury Cathedral was thwarted by slush - was unmasked as GRU colonel Anatoliy Chepiga, holder of the prestigious Hero of the Russian Federation medal.

Skripal's neice Viktoria Skripal, a regular Salisbury pundit on Russian TV, was yesterday reportedly injured in a car accident near Moscow when a wheel exploded.

Dawn Sturgess, 44, died and her boyfriend Charlie Rowley, 43, collapsed after he found a perfume bottle containing Novichok in Salisbury city centre in June.