BRUSSELS (Reuters) - NATO accused Russia on Thursday of trying to destabilise the West with new nuclear weapons, cyber attacks and covert action, including the poisoning of a Russian former double agent in Britain, that blurred the line between peace and war.

NATO Secretary-General Jens Stoltenberg addresses a news conference at the Alliance headquarters in Brussels, Belgium, March 15, 2018. REUTERS/Yves Herman

NATO Secretary-General Jens Stoltenberg told reporters the use of the Novichok nerve agent against Sergei Skripal and his daughter “happened against a backdrop of a reckless pattern of Russian behaviour over many years”.

Russia denies any involvement and says it is the U.S.-led Atlantic alliance that is a risk to peace in Europe.

Britain’s National Security Adviser Mark Sedwill told NATO envoys at a special meeting of the alliance’s governing North Atlantic Council that Russia was to blame.

“What happened in Salisbury was the latest in a clear pattern of reckless and unlawful behaviour by the Russian state,” Sedwill said in a statement he read to reporters after the meeting, referring to the English city where Skripal was attacked.

Sedwill said the attack “concerns the whole alliance” and that Britain would support allies who faced similar threats. Britain’s ambassador to NATO briefed the envoys on Wednesday.

Stoltenberg said Russia was mixing nuclear and conventional weapons in military doctrine and exercises, which lowered the threshold for launching nuclear attacks, and increasingly deploying “hybrid tactics” such as soldiers without insignia.

Stoltenberg listed Russia’s 2014 annexation of Crimea, its direct support for separatists in Ukraine, its military presence in Moldova and Georgia, meddling in Western elections and its involvement in the war in Syria as evidence of Russia’s threat.

He cited the development of new nuclear weapons, which President Vladimir Putin unveiled in a bellicose speech on March 1, as another worrying development.

“BLURRING THE LINE”

He also accused Moscow of a “blurring of the line between peace, crisis and war”, which he said was “destabilising and dangerous”.

Stoltenberg, who will meet British Foreign Secretary Boris Johnson on Monday in Brussels, stressed there had been no request from London to activate the Western military alliance’s mutual defence clause, but said Russia must be deterred.

“The UK will respond and is responding in a proportionate and measured way ... I fully support there is a need for a response, because there must be consequences when we see actions like those in Salisbury,” he said.

NATO has deployed significant ground forces to the Baltic countries and Poland to dissuade Russia from repeating any Crimea-like seizures.

Stoltenberg said there was little for NATO as an alliance to do immediately in response to the nerve agent attack, beyond giving Britain strong political support.