The UK has condemned the arrest of Russian dissident and opposition leader Alexei Navalny as he was sentenced to 15 days in prison on Monday (27 March).

Navalny, a vocal critic of President Vladimir Putin and Prime Minister Dmitry Medvedev, was arrested the day before at an anti-corruption rally in Moscow.

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He was detained alongside hundreds of protesters and journalists at the rally after Russian police declared the protest "illegal".

In a statement released by Britain's Foreign Office, a spokesperson said: "The UK is concerned by the detention on 26 March of hundreds of Russian citizens following organised protests, which included journalists and opposition leader Alexei Navalny.

"Russian citizens were exercising their fundamental rights to freedom of expression, association and peaceful assembly.

"The UK calls on the government of Russia to release citizens detained during peaceful demonstrations, and to comply with its international commitments in the Council of Europe and the Organization for Security and Co-operation in Europe."

The protests, which also took place at a number of locations across Russia, were triggered by Navalny's investigative reporting fund, which published damning allegations against Medvedev.

It detailed Medvedev's expansive property holdings, worth billions of roubles, listed under "puppet" charities and foundations.

Known as the Anti-Corruption Foundation, the website also published images of the politician's lavish holidays and expensive spending habits, after hacking group Anonymous infiltrated a private Twitter account.

Anti-Corruption Fund's revelations regarding Russian Prime Minister Dmitry Medvedev (with English subtitles).

Navalny has declared his intention to challenge Putin at next year's presidential elections, but in February he was convicted of fraud and handed down a five-year suspended sentence, meaning he was unable to take part in the race.

However rights groups have claimed the case was politically motivated to stifle Navalny's political ambitions.

Following Sunday's arrest and in addition to the 15-day sentence, Navalny was given a 20,000-rouble (£280) fine for disobeying police orders.

Navalny remained defiant however, tweeting an image from court which read: "The time will come when and we will judge them (but honestly)."