President Vladimir Putin on Tuesday wished British Prime Minister Boris Johnson a speedy recovery from the coronavirus, saying his "optimism and sense of humor" would help him get better.
"I would like to express my sincere support at this difficult moment for you," the Kremlin quoted Putin as saying in a message to Johnson.
"I am sure that your energy, optimism and sense of humor will help to defeat the disease."
Johnson, 55, was moved to intensive care on Monday evening, 10 days after he said he tested positive for coronavirus.
A senior cabinet minister said Johnson had been given oxygen but had not been put on a ventilator.
He was first admitted to hospital Sunday evening for tests for persistent symptoms of the virus.
The Russian president is handling his duties remotely, the Kremlin said last week, after the head of the country's main coronavirus hospital tested positive following a meeting with Putin.