Opposition leader’s detention came shortly after he announced a string of rallies across Russia over a pension reform.

Russian opposition leader Alexei Navalny has been detained outside his home in Moscow, according to his spokesperson who linked the arrest to plans to hold anti-government demonstrations next month.

“He is now in the Danilovsky police station. They did not say why he is being detained. They took his phone away,” Kira Yarmysh said on Twitter on Saturday.

In an interview to radio station Ekho Moskvy, Yarmysh said it is “probably linked” to Navalny’s call for protests against the Russian government’s unpopular pension reform on September 9.

In a blog post published earlier on Saturday, Navalny said the demonstrations would take place in the capital and “in almost a hundred other cities”.

The opposition politician has criticised the planned pension age increase, a first in nearly 90 years, that has led to a rare outburst of public anger.

Navalny was barred from taking part in Russia’s March presidential election [File: AP]

More than 2.8 million Russians have signed a petition against the reform backed by President Vladimir Putin‘s ruling party.

Navalny, who was barred from taking part in Russia‘s March presidential election, served a month in prison in June after organising demonstrations before Putin’s fourth inauguration in May.

He was freed from prison the same day the World Cup started in Russia.

The 42-year-old anti-corruption activist has faced a string of charges since becoming leading opposition figure campaigning against Putin’s rule at mass demonstrations in 2011 and 2012.