Vladimir Putin tightened his grip on power in Sunday elections blighted by allegations his regime had stuffed ballot boxes and stockpiled illegal chemical weapons.

The strongman looks set to become one of modern Russia’s longest-ever rulers after securing a fourth presidential term in a poll in which he main opponent was barred from running.

Exit polls suggest Mr Putin, 65, would take around three-quarters of the vote meaning he will not face a second run-off election. Videos from across Russia have emerged appearing to show officials slotting bulletins in to ballot boxes.

However, Mr Putin’s victory came after Foreign Secretary Boris Johnson said Russia had been perfecting and building up stocks of Novichok, the nerve agent used in the attempted murder of double agent Sergei Skripal in Salisbury, for a decade.

In a major escalation of allegations against the current Kremlin government, Mr Johnson told BBC’s The Andrew Marr Show: “We actually have evidence within the last 10 years that Russia has not only been investigating the delivery of nerve agents for the purposes of assassination, but has also been creating and stockpiling Novichok.”

Mr Putin’s supporters have repeatedly cast doubt on British claims about the Salisbury events, raising a series of increasingly outlandish conspiracy theories about the crime.

Russia’s ambassador to the EU, Vladimir Chizhov, suggested the nerve agent may have come from the Porton Down laboratory, which is about eight miles from Salisbury.

His government is facing what are expected to be a tough new round of UK financial measures to hit regime favourites in the pocket.

The SNP, which says Nicola Sturgeon has come under cyberattack from Kremlin online trolls, has called for a crackdown on Scottish shell firms used to launder dirty money out of the former Soviet Union.

Russian officials have accused the UK and its allies of “Russophobia” and suggested such bigotry helped increase turn-out in Sunday’s elections.

The host of a show of Kremlin propaganda outlet RT said expat Russians had voted in record numbers “thanks, highly likely, to the mobilizing power of UK Skripal bellicosity”.

The Herald:

Mr Putin addresses a victory rally

This is the former KGB officer’s fourth presidential term as president but he has been in effective control of the country in one post or another since he emerged from near complete obscurity in 1999.

Mr Putin was always expected to win Sunday’s elections, which could keep him in power for another six years. One of his main opponents, the reformer Boris Nemtsov, was killed outside the Kremlin in 2015. The chairman of the Boris Nemtsov Foundation on Sunday evening tweeted a picture of a ballot with the former deputy prime minister’s name scrawled across it. “My candidate’s not here,” he tweeted. “They killed him”

READ MORE: In detail, why Putin was always going to win

His other main potential opponent, the lawyer, nationalist and anti-corruption campaigner Alexei Navalny, was not allowed to stand. Mr Navalny had urged a boycott. With few opponents given any chance to make a realistic challenge, Putin officials focused on drumming up a big official headcount. Last night it appeared they had succeeded with turnout higher than in 2012.

Mr Putin on Sunday evening addressed supporters in the Manezh Square outside the Kremlin, telling them was he part of “their team”. He said: “It’s really important to attract those who voted for other candidates. We have to move fowarded. That is how we are bound to succeed.”

Defeated liberal Kseniya Sobchak, a former TV presenter whose father Anatoly was Mr Putin’s political mentor, was last night heading for a distance fourth place finish with just over one per cent of votes.

Nevertheless, she said standing had been worth it. “People have heard the truth, which they have not heard for many years,” she said.

The Herald:

Ms Sobchak voting on Sunday

Britain, meanwhile, has been lobbying for international support over the poisonings, which come a decade after another Russian exile, Alexander Litvinenko, was killed with a rare radioactive substance traced back to Russia.

Mr Johnson will travel to Brussels to brief foreign ministers from across the European Union at a meeting on Monday on the attempted assassinations before holding talks Nato secretary general Jens Stoltenberg.

Investigators from the Organisation for the Prohibition of Chemical Weapons are to visit the UK to take samples of Novichok, the substance used to attack Ms Skripal, 66, and his daughter Yulia, 33.

The team from The Hague will use international laboratories to carry out tests on the nerve agent.

Labour, meanwhile, changed tack after facing intense criticism for leaving open the possibility that Russia was being framed.

The Herald:

Mr Putin salutes supporters

Shadow chancellor John McDonnell said the Salisbury incident is “highly likely” to have been a state execution, and Russian president Vladimir Putin “is responsible” for the attack whether directly or through negligence.

READ MORE: In detail, why Putin was always going to win 

He told ITV One’s Peston on Sunday: “He is responsible whichever way you look at it, he is responsible and all the evidence points to him.”

He added: “We support exactly what the Prime Minister said and we condemn Russia for this, condemn them. I believe this is a pattern of behaviour we have seen.”