Martin McGuinness has called on people not to celebrate the death of Baroness Thatcher.
Street parties were held in republican parts of Londonderry and West Belfast following the former prime minister's death.
And for a second night crowds gathered in Belfast. A crowd of around 100 people disrupted traffic on the Falls Road, waving flags and sounding horns.
Mr McGuinness, Sinn Fein's Deputy First Minister at the Northern Ireland Assembly, tweeted: "Resist celebrating the death of Margaret Thatcher. She was not a peacemaker but it is a mistake to allow her death to poison our minds."
Unionists such as DUP First Minister Peter Robinson have praised her commitment to the UK but Sinn Fein president Gerry Adams accused her of pursuing "draconian, militaristic" policies which prolonged the conflict.
Her uncompromising stance over the hunger strikes in the Maze/Long Kesh prison in 1981 defined her as a republican hate figure. She refused to back down on her policy of criminalisation of IRA inmates. A total of 10 prisoners starved themselves to death in an attempt to secure prisoner of war-type privileges.
Baroness Thatcher also took a steadfast approach against any wider settlement with the IRA as violence regularly afflicted Northern Ireland. An IRA bomb in 1984 exploded at the Conservative Party conference in Brighton, killing four delegates and seriously injuring many others in an attempt to assassinate the premier.
DUP MLA Jonathan Bell said celebrations in Londonderry and on the Falls Road in Belfast were disappointing and "deeply inappropriate". "The response from Sinn Fein and republicans to the death of our former prime minister Margaret Thatcher, whom the IRA sought to murder, was both disappointing and disgusting," he added.
The Union flag is to be flown at half-mast from Belfast City Hall for the funeral, a DUP councillor confirmed. Hoisting the emblem is restricted to designated days following a vote at Belfast City Council last year which sparked weeks of violent protest.
William Humphrey said: "Whilst views of her premiership will continue to be debated there is no doubt that the vast majority of our citizens would wish that due recognition and respect should be paid to mark her passing ... I regret that I must express disgust that some people have chosen to take part in obscene public scenes of celebration at the passing of Lady Thatcher."