UK tells Russia to 'de-escalate tensions' with Ukraine
The British leader echoed concern from the G7 on Sunday about the build-up of Russian forces on the border, urging a diplomatic solution to the stand-off, his office said.
Johnson's intervention comes after a two-day meeting of the G7 nations in which the grouping's top diplomats warned Moscow of "massive consequences" if it invades the former Soviet state.
Direct contact between London and Moscow has been rare since London expelled dozens of Russian diplomats following a chemical weapon attack in the English city of Salisbury.
Britain blamed Russia for the 2018 attempted murder of former double agent Sergei Skripal and his daughter with the Cold War-era nerve agent Novichok.
It had already accused the Kremlin of being behind the radiation poisoning death of another former Russian agent, Alexander Litvinenko, in London in 2006.
Downing Street said Johnson told Putin of his "deep concern" at the Russian troop build-up on the border with Ukraine, which Moscow says is defensive.
In a statement, the Kremlin said that Putin responded to Johnson by condemning Kiev's "destructive line" and accusing Ukraine of "purposefully exacerbating the situation on the contact line" by using "heavy weapons and attack drones".
The Russian leader stressed that the tensions were taking place as NATO countries were actively involved militarily with Ukraine, calling for international agreements to rule out NATO advancing further the east and deployment of weapons threatening Russia in neighbouring states.
Johnson "reiterated the importance of working through diplomatic channels to deescalate tensions and identify durable solutions," the UK government statement said.
"The prime minister emphasised the UK's commitment to Ukraine's territorial integrity and sovereignty, and warned that any destabilising action would be a strategic mistake that would have significant consequences."
The G7, made up of Britain, Canada, France, Germany, Italy, Japan and the United States, unanimously condemned Russia and warned it of severe repercussions in similar language.
All options, including wide-ranging political and economic sanctions, were on the table if Russia ignores a diplomatic solution, officials indicated.