Almost daily protests have gripped Serbia since November, following the collapse of a railway station roof that killed 16 people.

The tragedy became a symbol of deep-rooted corruption in the Balkan nation, with demands for a transparent investigation growing into calls for early elections.

At their peak, the protests drew hundreds of thousands onto the streets.

But the mostly peaceful demonstrations deteriorated earlier this week when large groups of pro-government supporters – many masked and some armed with batons and fireworks – attacked protesters.