Close military encounters between Russia and the west have jumped to cold war levels, with 40 dangerous or sensitive incidents recorded in the past eight months alone, according to a report published on Monday.

The report, Dangerous Brinkmanship by the European Leadership Network, logs a series of “highly disturbing” incidents since the Ukrainian crisis began earlier this year, including an alarming near-collision between a Russian reconnaissance plane and a passenger plane taking off from Denmark in March with 132 passengers on board.

What made the incident especially dangerous was that the Russian plane did not have on its transponders, the usual method of signalling its presence to other aircraft.

The report by the London-based thinktank comes after a warning from former Soviet president Mikhail Gorbachev that the world is “on the brink of a new cold war”.

The encounters have taken place mainly around the Baltic Sea but also in the Black Sea and along the US and Canadian borders.

“We believe the nearly 40 incidents logged are a very serious development, not necessarily because they indicate a desire on the part of Russia to start a war but because they show a dangerous game of brinkmanship is being played, with the potential for unintended escalation in what is now the most serious security crisis in Europe since the cold war,” say the report’s authors Thomas Frear, Lukasz Kulesa and Ian Kearns.

Since the collapse of the Soviet Union in the early 1990s, Russian and Nato forces have routinely tested one another’s air defences, with both sending planes close to international borders to see how fast the other responds. But this year has seen not only a surge in such encounters but limits being pushed to new, more risky levels.

The US, Britain and other Nato allies accuse Russia of ramping up military action, but Moscow places the blame on the US and its European allies, accusing them of provoking the crisis in the Ukraine and through the imposition of sanctions on Russia. Gorbachev, normally a critic of Vladimir Putin, took the unusual step of siding with the Russian leader and called for new mechanisms for lowering tensions.

Some anti-war activists in the US and the west argue that Nato is hyping up encounters and risking all-out war.

The report authors urge the Russian leadership to “urgently re-evaluate the costs and risks of continuing its more assertive military posture”. They also call on all sides to exercise military and political restraint and improve military-to-military communication and transparency.

Nato logged up to late October more than 100 intercepts of Russian aircraft, three times more than last year.

These and other incidents add up to a highly disturbing picture of violations of national airspace, emergency scrambles, narrowly avoided mid-air collisions, close encounters at sea, and other dangerous actions happening on a regular basis over a very wide geographical area, the report says.

Among high-risk incidents it lists are: the abduction by Russia of an Estonian intelligence agent in September: a mock Russian bombing raid on a heavily populated Danish island; simulated cruise missile attacks by Russian bombers on the US and Canada; Canadian warships locking radar on approaching Russian aircraft in the Black Sea; and a US plane making unauthorised entry into Swedish airspace after being chased by Russian planes.

Estonian defence minister Sven Mikser said last week that while he did not see outright military conflict with Russia as likely, Russia had returned to cold war ways by stepping up incursions.

According to Lithuania’s defence ministry, Nato fighter jets around the Baltic states had been scrambled 86 times by mid-October, nearly twice as many as the whole of last year. Estonia has reported six breaches of its airspace by Russian aircraft this year, up from two in all of 2013. Latvia says it has sighted more than 40 Russian military vessels near its waters.

British general Sir John McColl, former deputy supreme allied commander in Europe, said the potential for miscalculation or escalation could be a matter not of if but when. While the recent increases in incidents were central high-level decisions, the physical execution of policy was delegated down.

“Junior commanders with highly capable equipment under their control will be interpreting broad direction using their initiative as circumstances develop in front of them. The potential for error and escalation is clear, and extremely dangerous; more a matter of when rather than if,” McColl said.

Former British defence secretary Des Browne shared the concern, singling out the near collision between the passenger plane and the warplane as well as the abduction of the Estonian, which he described as “a Russian incursion into Nato territory which had it got out of hand, could have had incalculable consequences”.

Kearns, who has been engaged with senior British foreign and defence policy makers for two decades, said: “We badly also need to negotiate a new crisis management arrangement with Russia to avoid a major unintentional escalation. The Chinese and Japanese have negotiated just such an arrangement in the East China Sea in the last few days. That is what we now need in Europe.’

China and Japan reached agreement on Friday on just such mechanisms in the East China Sea after similar tension. The two have been in dispute over tiny unpopulated islands controlled by Japan but claimed by Beijing and known as the Diaoyu in China and the Senkaku in Japan.

Three close encounters

Near mid-air collision with passenger plane On 3 March this year, an SAS passenger plane taking off from Copenhagen with 132 passengers bound for Rome had a close encounter with a Russian reconnaissance plane which did not transmit its position. A collision was only avoided because of good visibility and the alertness of the SAS pilots, according to the report. The incident, which happened 50 miles south-east of Malmo, in Sweden, was before the shooting down of the MH17 passenger plane over Ukraine. Russian-backed Ukrainian separatists were blamed for the July missile attack.

Simulated cruise missile attacks on North America In early September this year, Russian strategic bombers in the Labrador Sea near Canada practised cruise missile strikes. The Russian aircraft stayed out of Canada’s airspace but it was still a provocative move in light of the Nato summit at the time, according to the report. Cruise missiles launched from the Labrador Sea would have Ottawa, New York, Washington, Chicago and America’s Norfolk naval base in range.

Black Sea encounter On 7 September, the Canadian frigate Toronto was buzzed by a Russian aircraft in the Black Sea with the plane coming within 300 metres. The Toronto locked its radar on the Russian plane but took no further action as the Russian plane was not armed. The incident coincided with larger Russian larger naval combat training activities near Sevastopol. “Such aggressive behaviour, if repeated by an armed aircraft, could have resulted in the ship commander targeting the aircraft in an act of self-defence,” the report says.