Thousands of people around Russia have joined unauthorised rallies to protest against the detention of jailed opposition leader Alexei Navalny.
Demonstrators are calling for Navalny, who has been on hunger strike for weeks, to receive proper medical care.
He was jailed in February and is demanding medical attention for acute back pain and leg numbness.
The largest demonstration was in Moscow, but others took place in major cities around the country.
These included St Petersburg, Vladivostok in the Far East, a number of cities in Siberia, and the central city of Vladimir where Navalny is being held.
The opposition had hoped Wednesday's protests would be the largest in years, but reports suggest they have been smaller than those that took place shortly before Navalny was jailed.
More than 14,000 people protested in 29 cities, police said. This included 6,000 people who gathered in Moscow.
But estimates from monitoring groups tend to far exceed official police figures. One such group, OVD-Info, said more than 1,000 people had been detained nationwide.
'Fight for the future'
"This is one of the last gasps of a free Russia," one protester told Reuters news agency. "We came out for Alexei."
"This is a fight for the future," another demonstrator, Andrei Zamyatin, told AFP.
Others were less hopeful about the impact the mass action could have. "I don't think this protest can save Navalny," Alexander Butuzov told AFP.
"There would need to be at least 200,000 to 300,000 people in the streets," he said.
The protesters defied stark warnings from the authorities and a heavy police presence in most major cities.
"Any aggressive actions by participants in unauthorised public meetings, especially attempts to provoke clashes with law enforcement officials, will be regarded as a threat to public safety and immediately suppressed," the interior ministry said earlier this week.
In Moscow, riot police urged people to leave the protest area and formed barricades to try and contain the demonstrators' route.
They earlier cordoned off the area around Manezh exhibition hall, where Putin addressed both houses of parliament during his annual state of the nation speech.
On Monday, Navalny was moved to a prison hospital where the authorities said his condition was "satisfactory".
The FSIN prison service added that he was being examined by a doctor daily and had agreed to take vitamins.
But the 44-year-old's doctors warned he would "die within the next few days" if not given urgent medical attention for his back pain and leg numbness.
He started a hunger strike on 31 March in protest at not being able to see his own medical team. His doctors say recent blood test results indicate he could suffer kidney failure and go into cardiac arrest at any moment.
Navalny was poisoned with a nerve agent last August and only narrowly survived. After his transfer to intensive care in Berlin, toxicologists concluded that the poison was Russian weapons-grade Novichok.
Western governments blamed the Russian state for the attack, and Navalny accused President Vladimir Putin directly. The Kremlin denied any involvement and disputed the conclusion about Novichok.