Russia has lashed out after a Swiss warplane flew "dangerously close" to one of its passenger jets carrying a senior parliamentary delegation, although Switzerland defended it as a routine check.
The incident, which took place on Monday morning (local time), initially sparked a diplomatic spat between Moscow and Paris after the Russian foreign ministry claimed it was a French military jet and summoned France's envoy for an explanation.
Moscow later acknowledged the error and apologised to Paris through diplomatic channels.
The Swiss defence ministry confirmed the incident, saying one of its F-18 warplanes had approached the Russian craft for "a routine check".
A parliamentary delegation headed by Russian State Duma speaker Sergei Naryshkin were onboard the Russian plane en route to a meeting in Geneva, the Russian foreign ministry said.
Swiss defence ministry spokesman Peter Minder told AFP the incident had taken place in Swiss airspace over the city of Bienne, also called Biel or Bienna.
"It was a normal check by the Swiss air force... a close check," he said.
"We made visual contact with the pilot and noted the registration. Everything was in order. It was a verification, a routine check."
Under terms of an agreement linked to the protection of Geneva, Switzerland has permission to fly over the skies of eastern France, the French foreign ministry said.
Russia had initially blamed France, with the foreign ministry in Moscow saying it had summoned French envoy Jean-Maurice Ripert to "give an explanation" for the incident.
"The ambassador was made aware of Russia's deep concern over what happened," it said.
"Actions like these by Paris undermine the possibility of using France as a place for multilateral meetings and talks."
But France rebuffed the claim.
"We deplore that the French ambassador in Moscow was called in instantly," the French defence and foreign affairs ministry said. "The necessary explanations have been handed on to the Russian authorities."
During the evening, Russian foreign ministry spokeswoman Maria Zakharova confirmed that Moscow had apologised to Paris through diplomatic channels, but had demanded an explanation from Switzerland.
"We have to work out what happened and why it was done," she said in televised comments.
Yevgenia Chugunova, spokeswoman for the Russian speaker Naryshkin, told AFP that the warplane flew so close that delegation members could take a picture.
"I can confirm that this incident involving a French military plane happened this morning," she said. "We saw it very close."
Naryshkin, who is on both the EU and US blacklists for publicly supporting the deployment of Russian forces to Ukraine and the annexation of Crimea, told Russian agencies he was aware of what happened although he did not see the warplane himself.
Sergei Gavrilov, another delegation member, told TASS news agency that the approach took place "at the altitude of 3,700 metres above the Swiss border" and called it an "unfriendly act by NATO".
Switzerland is a neutral country and is not a member of the North Atlantic alliance.