Putin's critic Navalny hospitalised with 'acute allergic reaction' after being arrested

Russian opposition leader Alexei Navalny, who was arrested last week, has been hospitalised with an "acute allergic reaction", and his spokesman said on Sunday he may have been affected by an "unknown chemical substance".

"We cannot rule out toxic damage to the skin and mucous membranes by an unknown chemical substance with the help of a certain 'third person'," Navalny's spokesperson Kira Yarmysh quoted a Facebook post by the Kremlin critic's personal doctor as saying.

Navalny, the most vocal opposition leader, was detained by police on Wednesday after he gave a call for protests over the weekend against the disqualification of opposition candidates for Russian municipal elections, CNN reported.

Navalny wrote on Instagram that he was detained as he left his apartment to go on a jog.

"People are right when they say that sport is not always good for your health," he quipped.

"I have been detained and am now at a police station wearing shorts like a stupid man," he added.

He was handed down a 30-day prison sentence for allegedly violating the country's protest laws.

Meanwhile, anti-government demonstrations broke out in Moscow with groups of people marching on the streets over the weekend. The police detained more than 1,000 people on Saturday.

Navalny, who was considered as the only real challenger to President Vladimir Putin, was barred from running in the Russian presidential election in 2017. He was then sentenced to 30 days in jail. He was also attacked with an antiseptic green dye which damaged his vision in one eye.