Russians honour slain Kremlin critic Boris Nemtsov

Thousands of Russians marched through central Moscow on Saturday in memory of opposition politician Boris Nemtsov who was gunned down near the Kremlin a year ago in the highest-profile assassination of Vladimir Putin's rule.

On a bright sunny afternoon opposition supporters thronged the streets amid heightened police security as a helicopter hovered overhead.

Some marchers carried Russian flags, some black ribbons, placards, flowers and Nemtsov's portraits. Others chanted: "Russia will be free" and "Russia without Putin."

Some 20,000 joined the march, according to estimates from AFP correspondents. Moscow police, which are often accused of downplaying the popularity of opposition events, said 7,500 showed up.

Many protesters said the situation in Russia had got worse since the opposition politician's murder.

"Aggression and xenophobia have gone through the roof," Anastasia Osipova told AFP.

"Over the past year things have become so much worse, both when it comes to the economy and freedom of speech," said the 20-year-old, clutching an EU flag.

Yevgeny Mishchenko, 41, sounded a similar note.

- 'Russia's nightmare' -

"The authorities, this regime killed Nemtsov," he said. "The economic situation is worsening. Support for the authorities is crumbling. This will all end in a civil war, like a hundred years ago."

In Putin's hometown of Saint Petersburg, some 4,000 people turned out to honour Nemtsov. "Putin is Russia's nightmare", one placard read, while some chanted "Putin get out."

Russia's annexation of Crimea, fighting in eastern Ukraine and Moscow's confrontation with the West have left the country deeply polarised.

Most of the population -- who critics say have been under the spell of pro-Kremlin propaganda -- support Putin despite mounting economic troubles, while a minority says Russia is hurtling towards catastrophe.

People also brought flowers and candles to the bridge near the Kremlin walls where Nemtsov, a jovial 55-year-old with a mop of black curly hair, was killed.

US ambassador John Tefft was among those who came to pay their respects, laying a wreath with a ribbon saying "From the American people."

Smaller commemorative events took place across Russia.

Nemtsov's daughter Zhanna was due to launch a foundation in her father's name in London later on Saturday along with ex-tycoon Mikhail Khodorkovsky, an opposition leader who spent a decade in prison.

Britain's Europe Minister David Lidington urged the Russian government "to ensure that those responsible for this appalling crime are brought to justice."

On the eve of the anniversary, lawmaker Dmitry Gudkov, one of the few independent voices in Russian parliament, said he suggested that deputies observe a moment of silence in Nemtsov's memory but most of his colleagues refused.

Nemtsov, a former deputy prime minister in the government of Boris Yeltsin, was gunned down shortly before midnight on February 27, 2015, while walking across a bridge a short distance from the Kremlin with his Ukrainian model girlfriend.

- 'Who dared?' -

Putin, whose rule has seen the steady suppression of independent media and opposition parties, promised an all-out effort to catch the killers.

"Who dared?" a furious Putin asked his aides after Nemtsov was hit in the back by four fatal shots, the top opposition Novaya Gazeta reported this week.

Within weeks five men -- all Chechens from Russia's restive North Caucasus -- were arrested and charged with murder.

The five detainees -- including Zaur Dadayev, a member of a Chechen interior ministry battalion accused of being the gunman -- are now awaiting trial for what investigators say was a carefully planned contract killing.

But Nemtsov's family and allies insist the authorities have failed to bring the masterminds to justice and point the finger of blame at Chechnya's Moscow-backed strongman Ramzan Kadyrov -- and the Kremlin itself.

Earlier this month, men -- apparently from the North Caucasus -- threw a cake at Nemtsov's ally, former prime minister-turned-opposition activist Mikhail Kasyanov and shouted threats at him.

The Kremlin downplayed the cake-throwing attack, saying it should be in no way linked to Kadyrov.

Two weeks later unidentified attackers threw a cake at top opposition leader Alexei Navalny.

Both attacks took place shortly after the Chechen strongman posted an Instagram image of Kasyanov in the crosshairs of a sniper's rifle and called the opposition "enemies of the people."

"They are trying to make the harassment of the opposition look like a farce but this does not mean that directors of the cheap comedies would refuse more brutal genres," liberal daily Vedomosti said in an editorial.