MOSCOW — Aleksei A. Navalny, the imprisoned Russian opposition leader, ended a three-week hunger strike on Friday that had embarrassed the Kremlin, drew international criticism and sparked protests at home.
The 24-day hunger strike, which Mr. Navalny said had left him so skinny he looked like a “skeleton, swaying, walking in its cell,” became the latest battle in a yearslong, high-stakes competition between President Vladimir V. Putin and his most prominent domestic political opponent.
Mr. Putin refuses even to speak Mr. Navalny’s name while the police and prosecutors harry his political organization with arrests and, this month, a move to ban it outright. Mr. Navalny is serving a prison sentence of more than two years for a parole violation of a conviction he says was politically motivated.
But even in prison he managed to confound Mr. Putin with a quandary: either concede to his demands for medical treatment by his personal doctors or risk creating a martyr.
Through the years Mr. Navalny has run a highly effective investigative unit that has embarrassed Mr. Putin and discredited his government with slickly produced videos exposing corruption at the highest ranks. He routinely refers to Mr. Putin’s United Russia party as a gang of “crooks and thieves.”
Mr. Navalny has also continued to set the agenda for the political opposition ahead of parliamentary elections scheduled for the fall. His organization turned out tens of thousands of street protesters on Wednesday, stealing some of the limelight from Mr. Putin’s annual state of the nation address.
Mr. Navalny said he halted his hunger strike on the advice of his doctors and because his demands had been partially met.
Mr. Navalny blamed the Russian government, saying that Novichok, a rare nerve agent only manufactured in Russia and the Soviet Union before it broke up, had been placed in his underwear in a hotel room last August. At the time, he was organizing his political group for local elections. The Kremlin denied any role in the poisoning.
Mr. Navalny was medically evacuated to Germany in a coma, recovered and returned to Russia in January, where he was arrested at the airport.
In prison, he reported back pain and numbness in his legs and arms. Earlier this month, tests showed signs of possible kidney failure that could lead to a lethal irregularity in Mr. Navalny’s heartbeat, his doctors said.
Prison authorities never allowed access for Mr. Navalny’s personal doctor. They did move him from his cell, first to a prison hospital then a civilian hospital, and this week allowed specialists to examine him.
“Doctors whom I fully trust made a statement that we have achieved enough for me to stop my fast,” Mr. Navalny said in a statement posted on his Instagram account on Friday. He said doctors had also advised him that if he continued the hunger strike, “there will be nobody left to treat.”
Mr. Navalny said he also broke his fast because some supporters had announced hunger strikes in solidarity with him, and he did not want to risk their health.
Mr. Navalny’s personal doctors issued a statement Thursday outlining the health care prison authorities had allowed after his transfer to a civilian hospital, including examinations by independent neurologists. The doctors said they had also received access to his test results, partially fulfilling the demands of the hunger strike.
The statement signed by Mr. Navalny’s personal doctor, Anastasia Vasilyeva, and four specialists said they had not lifted their request to examine Mr. Navalny in person. But enough had been done, they said, to justify halting the strike.
The extended hunger strike, however risky for Mr. Navalny personally, has kept his case on the agenda of Western governments despite a Russian military buildup on the border with Ukraine.
The United States national security adviser, Jake Sullivan, this month said that the Russian government would face “consequences if Mr. Navalny dies.” Foreign Minister Jean-Yves Le Drian of France also expressed concern and put the Russian government on notice: “There is a major responsibility here for President Putin,” he said.
In domestic politics, Mr. Navalny’s hunger strike and deteriorating health prompted street protests on Wednesday in cities across Russia.
The protests brought riot police officers out in force in Russian cities on a day when Mr. Putin intended to highlight in his state of the nation speech a hopeful message of economic growth as the country emerged from the coronavirus pandemic. By the end of the day, police had detained nearly 1,500 demonstrators nationwide.