Prime Minister Boris Johnson has led the political condemnation after violence broke out on the streets of Belfast, after a bus was hijacked and set on fire in an interface area.
The bus was set alight after being pelted with petrol bombs at the junction of Lanark Way and Shankill Road in west Belfast, the PSNI said.
It was one of a number of incidents on Wednesday evening that took place on the peace line street that links the loyalist Shankill Road with the nationalist Springfield Road.
Writing on Twitter, Mr Johnson said: "I am deeply concerned by the scenes of violence in Northern Ireland, especially attacks on PSNI who are protecting the public and businesses, attacks on a bus driver and the assault of a journalist.
"The way to resolve differences is through dialogue, not violence or criminality."
Stones were thrown at police while Belfast Telegraph photographer Kevin Scott was assaulted nearby on Wednesday evening.
Later on Wednesday night, the gates of the peace line on Lanark Way were opened, leading to clashes between loyalists and nationalists.
Social media footage captured petrol bombs being thrown from both sides of the wall.
First Minister Arlene Foster condemned the attacks on Twitter, saying: "There is no justification for violence. It is wrong and should stop."
I am deeply concerned by the scenes of violence in Northern Ireland, especially attacks on PSNI who are protecting the public and businesses, attacks on a bus driver and the assault of a journalist. The way to resolve differences is through dialogue, not violence or criminality.— Boris Johnson (@BorisJohnson) April 7, 2021
The DUP leader also hit out at footage showing a Translink bus being targeted while passengers and a bus driver were on board.
"This is not protest. This is vandalism and attempted murder. These actions do not represent unionism or loyalism. They are an embarrassment to Northern Ireland and only serve to take the focus off the real law breakers in Sinn Fein," said Mrs Foster.
"My thoughts are with the bus driver."
In response to Mrs Foster's tweet, Justice Minister Naomi Long took a swipe at the First Minister's comments, saying: "These are 'real law breakers', burning buses, terrorising passengers and attacking police.
"Let's focus on that and getting this stopped before someone loses their life."
The incident was also roundly condemned by the SDLP, with its west Belfast representative, Paul Doherty tweeting: "I've spent this evening trying to talk sense into many young people engaging in violence at Lanark Way and on the Springfield Road. This needs to end now before someone is seriously hurt or worse, killed."
Sinn Fein's Paul Maskey insisted the latest outbreak of loyalist disorder was "being whipped up by the reckless rhetoric of political unionism".
"It needs to stop immediately before someone is killed or seriously injured," he said.
“We need to see political leadership stepping up the plate to do all in its power to reduce tension and bring these actions to an end.”
These are "real law breakers", burning buses, terrorising passengers and attacking police.— Naomi Long MLA (@naomi_long) April 7, 2021
Let's focus on that and getting this stopped before someone loses their life. https://t.co/dZ5UwCflzb
Wednesday night's violence follows several nights of unrest in loyalist communities amid tensions over the Northern Ireland Protocol on Brexit and the PSNI's handling of alleged coronavirus regulation breaches by Sinn Fein at the funeral of republican Bobby Storey.
PSNI Chief Constable Simon Byrne also made a plea for the violence to end late on Wednesday.
"The ongoing street disorder must stop," he tweeted.
"I am open to dialogue with anyone who is willing to work with me to resolve the issues facing our community."
He added: "My message to those engaged in violence tonight is go home before someone is seriously injured, violence is not the answer."