Angry scuffles broke out at Stormont today after Mr David Trimble and Mr Mark Durkan were re-elected as First and Deputy First Minister.
Police officers and security guards moved in to keep rival factions apart as furious nationalist and unionist politicians surged towards each other.
Members of the DUP and the nationalist SDLP had to be restrained as Mr Trimble vainly tried to speak to the press.
His comments were drowned out by the jeers of "traitor" and "cheat" by members of the DUP.
They were furious Mr Trimble had been re-elected on the back of votes from the Alliance Party, three of whose members re-designated themselves as unionist to secure a majority for Mr Trimble.
Republicans were later drawn into the melee.
DUP leader the Rev Ian Paisley claimed a member of the SDLP provoked the ugly exchange by punching a member of his party.
"The time has come to name the people, whom they saw quite clearly start the trouble."
Sinn Féin's Martin McGuinness hit back, claiming "the DUP enjoyed themselves on Friday but they did not enjoy themselves today and that resulted in the unseemly scenes we saw today".
Mr Sean Farren, an SDLP minister at the Assembly, claimed the DUP was to blame for the flare-up.
Mr Trimble later denounced the clashes, saying: "We will not allow ourselves to be distracted by the sort of mob violence some parties descended to".
Ninety-nine Assembly members participated in the vote for the First and Deputy First Minister, with 60 unionists taking part following the Alliance re-designations.
Crucially, 31 unionist MLAs backed Mr Trimble and Mr Durkan to fill the posts - 51.7 per cent of those present. All 38 nationalists present voted in favour of the motion.
Three Alliance Party MLAs earlier successfully re-designated themselves as unionist to secure the unionist majority Mr Trimble needed to win the vote.
Party leader Mr David Ford, deputy leader Ms Eileen Bell and former party chief Mr Sean Neeson temporarily re-aligned themselves.
PA