The disturbances took place on both sides of the interface, with attempts made to close the gate as officers tried to contain the violence.
The PSNI confirmed after 7pm tonight that crowds had gathered at the junction of Lanark Way and Shankill Road in west Belfast.
Mr Johnson said: "The way to resolve differences is through dialogue, not violence or criminality".
"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.
And Deputy First Minister Michelle O'Neill tweeted that the "violence and street disorder" was causing "huge distress in local communities at this time".
In an interview with The Sunday Independent, Campbell claimed First Minister and DUP leader Arlene Foster had informed the LCC that collapsing the Executive was within her party's "thinking", but only in the event that all other paths to ditch the protocol had been exhausted.
The Police Service of Northern Ireland has said some of the violence was influenced by "criminal elements" who helped to orchestrate the attacks. "It is wrong and should stop".
The unrest started last week after the Northern Ireland prosecutor's office refused to charge members of the Sinn Fein National Republican Party, who under coronavirus restrictions attended the funeral of former member of Provisional Irish Republican Army (IRA) Bobby Storey, who fought for separation from the United Kingdom. This is vandalism and attempted murder.
Stormont Education Minister Peter Weir was responding to earlier comments from David Campbell, chairman of the Loyalist Communities Council (LCC), an umbrella group representing loyalist paramilitary groups. "They. only serve to take the focus off the real law breakers in Sinn Féin", she posted on social media. "My thoughts are with the bus driver". His Irish counterpart, Micheál Martin, called on Dublin, London and all parties in Northern Ireland to work together to ease tensions and restore calm. As SkyNews reported, more than 40 police officers were injured and nine people were detained since the outbreak of the new unrest.
Plans to recall the Assembly were already underway after Alliance Party leader Naomi Long secured the required support of 30 members to force a return.
The violence has been blamed on anger in response to a decision by the Public Prosecution Service not to pursue prosecutions against members of Sinn Fein who attended the funeral of Mr Storey a year ago despite restrictions over gatherings, as well as Brexit and localised issues in the south-east Antrim area.