LONDON: UK Prime Minister Boris Johnson on Wednesday said he was deeply concerned by scenes of violence in Northern Ireland after crowds of youths in a pro-British area of Belfast set a hijacked bus on fire and attacked police with stones.

"I am deeply concerned by the scenes of violence in Northern Ireland, especially attacks on PSNI (Police Service of Northern Ireland) who are protecting the public and businesses, attacks on a bus driver and the assault of a journalist," Johnson said in a tweet.

"The way to resolve differences is through dialogue, not violence or criminality."