Russian warplanes are risking the security of civilian passengers as they play a dangerous game designed to test Western air defences, according to Nato’s secretary general.

The Russian bombers, which fly over international and European airspace, do not follow agreed safety procedures, designed to minimise the risk of collisions, Jens Stoltenberg has said.

Nato jets have intercepted more than 100 Russian aircraft this year alone, compared to 13 similar such incidents in 2013.

Mr Stoltenberg told The Telegraph: "The problem is that many of the Russian pilots don’t turn on their transponders, they don’t file their flight plans and they don’t communicate with civilian air traffic control.

“This poses a risk to civilian air traffic and therefore this is a problem, especially when the Russian activity increases – because they have more Russian military planes in the air."

Back in March a Scandinavian Airlines plane and a Russian surveillance plane came within 90 metres of each other just outside of the Swedish city of Malmo, as the military plane had not contacted air traffic controllers or switched on its transponder.

Disaster was only averted thanks to the Scandinavian pilot’s quick evasive action.

Nato's evolution Show all 7 1 /7 Nato's evolution Nato's evolution Nato countries How the Nato group appeared in 1952 i100 Nato's evolution Nato countries In 1955, the country then known as West Germany joined Nato. i100 Nato's evolution Nato countries In the early Eighties, Spain joins Nato. i100 Nato's evolution Nato countries A re-unified Germany joins Nato. i100 Nato's evolution Nato countries The Czech Republic, Hungary and Poland become the first former Soviet bloc states to join Nato, moving the alliance's borders some 400 miles towards Russia. i100 Nato's evolution 2004.jpg Bulgaria, Estonia, Lithuania, Latvia, Romania, Slovakia and Slovenia are made new members. i100 Nato's evolution Nato countries At Nato's 60th anniversary summit, Albania and Croatia are formally inducted into group - increasing its membership to 28. i100

Mr Stoltenberg’s intervention comes after the European Leadership Network (ELN) published a report earlier this month that found almost 40 close encounters had occurred between Nato, Russian and civilian aircraft in the past eight months.

The ELN condemned Russia’s “brinkmanship” under the leadership of Vladimir Putin.