Clashes between rival groups of protesters in Serbia left dozens injured overnight, police said on Thursday, as months of anti-government demonstrations boiled over into street violence for a second night, writes The Guardian.

“A wave of anti-corruption protests has gripped Serbia since November, when the collapse of the Novi Sad railway station roof killed 16 people, a tragedy widely blamed on entrenched corruption.

Protesters again gathered in several cities across Serbia late on Wednesday, mainly in response to an attack by ruling party supporters on demonstrators in the town of Vrbas, about 160km (100 miles) north of the capital, Belgrade.

For the second night running, large groups of pro-government supporters, most wearing masks, confronted protesters. The two groups hurled bottles, stones and fireworks at each other.

Police arrested nearly 50 people across the country, and about 30 riot police were injured. The worst violence was reported in parts of Belgrade and Novi Sad, where the protest movement first began.

One man, later identified as a military police officer, fired a pistol into the air as protesters approached the ruling party’s offices in Novi Sad, causing panic.

Footage also appeared to show supporters of the ruling Serbian Progressive party launching fireworks at protesters gathered outside the party’s headquarters there. Police intervened with teargas, and stun grenades could also be heard.

Frustrated with government inaction, protesters have demanded an investigation into the Novi Sad tragedy and piled pressure on the Serbian president, Aleksandar Vučić, to call early elections”.