Protesters today blocked roads in Belfast, Northern Ireland, and set fire to vehicles, including a bus, in the aftermath of a bloody knife attack attributed to a Sudanese refugee, French News Agency (AFP) reporters and British media reported.

The local police command and British authorities have repeatedly appealed for calm and restraint in the wake of the attack, the video of which has shocked public opinion.

A video of the attack, with stark images, circulated on social media. In it, the attacker is seen sitting on a bleeding man lying on the ground, trying to cut his throat. Three men can be seen intervening, one of whom overpowered the attacker by hitting him with a bat.

The alleged perpetrator of last night’s attack, aged 30 according to police, has been arrested for attempted murder. Police said he was Sudanese after initially saying he was “possibly Somali”.

The victim, in his early 40s, is being treated in a critical condition.

As of 7pm this evening (local time, 9pm in the UK), hundreds of protesters – including many wearing hoods – had begun to gather in various parts of Belfast. Pillars of smoke were rising in the city sky, where police helicopters could be seen, according to AFP.