Thousands of Russians have been taking part in unauthorised protests to demand the release of the jailed opposition leader Alexei Navalny.

More than 5,000 people have been detained, a monitoring group says. In Moscow police closed metro stations and blocked off the city centre.

Mr Navalny was jailed on his return to Russia after recovering from an attempt to kill him with a nerve agent.

He blames the security services for the attack but the Kremlin denies this.

The opposition figure was arrested after arriving in Moscow from Germany, where he spent months recovering from the near-fatal incident.

Russian authorities say Mr Navalny was supposed to report to police regularly because of a suspended sentence for embezzlement.

Mr Navalny has denounced his detention as "blatantly illegal", saying the authorities had allowed him to travel to Berlin for treatment for the Novichok poisoning, which happened in Russia last August.

Mr Navalny has blamed state security agents under Mr Putin's orders for the attempt on his life and investigative journalists have named Russian FSB agents suspected of the poisoning. But the Kremlin denies involvement and disputes the conclusion, by Western weapons experts, that Novichok was used.

Meanwhile, Russian President Vladimir Putin has denied reports he is the owner of a vast palace on the Black Sea, as alleged by Mr Navalny in a video that has gone viral in Russia and has been watched more than 100m times.

It's risky protesting in Russia. Even if you escape the police batons you can be fired, face a hefty fine or criminal prosecution.

So the fact that people turned out for a second weekend, right across Russia, is significant - the fact that there were fewer than last week, unsurprising.

By blocking off central Moscow, the authorities were trying to prevent a large crowd gathering in one place and so play down the scale of dissent. Instead, they got protesters marching along main city streets to the hoots of passing cars whose passengers waved victory signs in support.

Shopkeepers were drawn to their windows to watch and, in one beauty salon, women in hairnets stood filming on their phones as the crowd filed past.

Most protesters I spoke to said they weren't fans or followers of Alexei Navalny in particular, but they are shocked at how he's been treated. They described him as a symbol of resistance and talked of their own desire for change.

None of this means that Vladimir Putin is about to be ousted - he still has significant support. But after two decades in power, the shine has begun to rub off his presidency.

Where were the protests?

In Moscow the BBC's Sarah Rainsford says protesters played cat-and-mouse with police, getting up close to officers before retreating to safety. Police snatch squads pulled some protesters through the lines of riot shields. Footage showed a stream of people being escorted on to buses by riot police.

Protesters then attempted to reach the Matrosskaya Tishina prison where Mr Navalny is being held.

Mr Navalny's wife, Yulia Navalnaya, was among those detained at Sunday's protest. She was later released.

Ahead of the protests she posted on Instagram: "If we stay quiet, then they could come for any of us tomorrow."

Police said the protests were illegal and Russian authorities warned that the gatherings could spread the coronavirus.

A 40-year-old protester in Moscow told Reuters: "I understand that I live in a totally lawless state. In a police state, with no independent courts. In a country ruled by corruption. I would like to live differently," she said.

In St Petersburg, Mr Putin's home city, a crowd gathered in a central square and chanted: "Down with the Tsar."

Rallies in support of Mr Navalny also took place in eastern Russia. In the Siberian city of Novosibirsk, at least 2,000 people marched through the city chanting "Freedom" and "Putin is a thief".

In Yakutsk, where temperatures fell to -40C, a protester named Ivan said it was the first rally he had attended.

"I am tired of the despotism and lawlessness of the authorities. No questions have been answered. I want clarity, openness, and change. This is what made me come here," he said.

Further rallies saw about 1,000 people demonstrate in Omsk, also in Siberia, and about 7,000 people protest in Yekaterinburg in the Ural region, according to local media reports.

The OVD-Info monitoring group said police had detained more than 5,000 people at protests in 86 cities across the country. They included 1,608 held in Moscow and 1,122 in St Petersburg.

Later on Sunday, Mr Navalny's Moscow campaign headquarters announced the end of the day's protests and called on supporters to attend a rally on Tuesday at a Moscow court where a ruling will be made on Mr Navalny's detention.

A number of close associates of Mr Navalny have been detained since last week and others, including his brother and Pussy Riot activist Maria Alyokhina, have been put under house arrest.

The chief editor of a Russian website specialising in human rights, Sergei Smirnov, was also arrested outside his home on Saturday. News of his detention, apparently over allegations he participated in last week's protests, has been condemned by other journalists.

In Moscow, police have reportedly been struggling to find space in jail for supporters of the opposition leader.

What reaction has there been?

In a tweet, the EU's foreign policy chief, Josep Borrell, said he deplored the "widespread detentions and disproportionate use of force".

The new US secretary of state, Antony Blinken, condemned "the persistent use of harsh tactics against peaceful protesters and journalists".

He called for Mr Navalny and other opposition supporters to be released.

In response, the Russian foreign ministry accused the US of "gross interference" in its internal affairs and of using "online platforms" to promote the protests.