A Moscow court rejected Russian opposition leader Alexei Navalny's appeal against his prison sentence on Saturday, upholding a ruling that could see the Kremlin critic sent to a forced labour camp for nearly three years.

Navalny, who is the focus of multiple ongoing legal proceedings, was also found guilty of defamation in a separate case.

Speaking before the verdict, Navalny urged Russians to stand up to the Kremlin in a fiery speech mixing references to the Bible and Harry Potter.

A lower court sentenced Navalny earlier this month to two years and eight months in prison for violating terms of his probation while recuperating in Germany from a nerve agent poisoning that he blames on the Kremlin. Russian authorities have rejected the accusation.

Navalny, 44, an anti-corruption crusader and President Vladimir Putin’s most vocal critic, appealed the prison sentence and asked to be released. The Moscow City Court's judge on Saturday only slightly reduced his sentence to just over 2 and a half years in prison, ruling that a month-and-half Navalny spent under house arrest in early 2015 will be deducted from his sentence.

EU intervention

The two hearings come as the European Court of Human Rights (ECHR) this week called for the release of the 44-year-old Russian anti-corruption activist, arguing a risk is posed to the life of the opposition politician who survived a Novichok poisoning last year.

The intervention was immediately rejected by Moscow, which had already swept aside calls from the European Union for the cases against Navalny to be dropped, despite the threat of sanctions.

Returning to Russia in January from a convalescence in Germany, Navalny was arrested on arrival at the airport and was sentenced on February 2 to two years and eight months in prison.

The court converted a suspended prison sentence for fraud dating from 2014 into a firm sentence for violating his parole conditions.

It was this judgment that was being considered on appeal on Saturday morning in a Moscow court.

Present at the hearing, the opponent rejected the charge, saying he never wanted to evade the Russian authorities by going to Germany and warned them of his return.

"I bought a ticket and told everyone I was going home... It's just absurd," he told the judge, according to an AFP journalist present at the court.

The prosecutor retorted by saying that the opponent had "openly and brazenly" defied the law and that he wants to be granted an "exclusive" right of authorisation.

Ulyana Solopova, a spokeswoman for the Moscow courthouse, told AFP that the prison services will be free to transfer the opponent to one of Russia's many labour camps if the February 2 decision is confirmed.

Further legal action

In addition, Navalny appeared before another judge on Saturday afternoon in a trial for allegedly defaming a World War II veteran.

He was found guilty, and fined around 850,000 roubles (9,500 euros).

As a legacy of the Soviet Union, most prison sentences in Russia are served in prison camps, sometimes far from anywhere. Prisoners are required to work, usually in sewing or furniture-making workshops.

Prison conditions are also regularly denounced by human rights activists.

Navalny, whose incarceration in January led to three days of demonstrations repressed by the police, denounces fabricated legal proceedings and has spent previous hearings defying the court.

According to him, the Kremlin wants to throw him in prison to silence him, after failing to kill him by poisoning him in August last year. Moscow rejects these accusations.

Other cases are ongoing. In particular, a defamation suit has been filed against Navalny by oligarch Yevgeny Prigozhin, reputed to be close to President Vladimir Putin.

He is also being investigated for fraud, a case currently under investigation in which the maximum sentence is 10 years in prison.

The EU and the United States have made repeated calls for Navalny's release while the opponent's collaborators have urged the West to punish high-ranking Russian officials close to Putin.

Moscow sees this as "interference" in his affairs and has threatened Europeans with reprisals.

Navalny and his supporters plan to organise new demonstrations against the government in the spring and summer in the run-up to parliamentary elections.