The RUC last night used water cannons to disperse a loyalist crowd of more than 100 who attacked nationalist homes in north Belfast.
A police spokesman said the trouble began when loyalists from the Gunnell Hill area began throwing missiles at houses belonging to nationalists. Both sides blamed each other for the violence.
In a separate incident, Catholic children attending a community play on the Crumlin Road had to be evacuated at about 8 p.m. when two home-made bombs were thrown at the Brookfield Complex. A caller from the Loyalist Red Hand Defenders contacted a Belfast newsroom to claim responsibility.
In west Belfast, a 20-year-old man was taken to hospital after being shot in both feet. He was attacked in an alley off Beechmount Crescent.
Earlier, it was reported that pressure was mounting on the Northern Secretary, Dr John Reid, to declare the UDA ceasefire over after the killing of a young Protestant man and further pipe-bomb attacks on Catholic property.
The Red Hand Defenders, a cover name used in the past by both the UDA and the LVF, claimed responsibility for the killing of Mr Gavin Brett (18) in Glengormley on Sunday.
At the beginning of July the group admitted killing an Antrim man, Mr Ciaran Cummings, and shortly afterwards it claimed responsibility for an attack on a Catholic community centre in north Belfast. Nationalist politicians have blamed the UDA for these attacks as well as for more than 100 pipe-bombings since the start of the year.
Dr Reid announced that he is to hold an urgent meeting with his security advisers today to address the killing of Mr Brett and others.
The Sinn Fein president, Mr Gerry Adams, said the killing of Mr Brett was further proof that the UDA ceasefire had ended. He demanded that the British government and RUC admit this.
Speaking after a meeting with the RUC Chief Constable, an SDLP delegation said it had presented him with "compelling evidence" of the UDA's belligerence. Mr Alex Attwood, the party chairman, said they had told Sir Ronnie Flanagan that in three of six of the UDA's command areas the organisation had demonstrably abandoned its ceasefires.
Sir Ronnie meanwhile said he could not rule out UDA involvement in the killing of Mr Brett. He described the Red Hand Defenders as "a flag of convenience for the lowest form of so-called loyalist life".
He said there was growing evidence that members of the UDA were behind attacks and were also orchestrating violence. However, he doubted that the UDA's central command had reached an "official" decision to abandon its ceasefire.
Mr John White, a spokesman for the UDA-linked Ulster Democratic Party, said that while individual members of the UDA might be involved in attacks, the group's leadership was behind the peace process.
The Ulster Unionist leader, Mr David Trimble, called on loyalists to end their violence.
The Minister for Foreign Affairs, Mr Cowen, has said he was appalled at the "despicable and cowardly" murder of Mr Brett.
Mr Cowen said there was little doubt that this was yet another sectarian attack. He added: "There is no place in a civilised society for such activity. The perpetrators of this heinous act must not be allowed to succeed in their attempts to return to the devastation and violence of the past."
The Minister called on all sides to exercise restraint and urged everyone with influence to redouble their efforts to bring about a society "where such evil deeds will be consigned forever to the past".
The Fine Gael leader, Mr Michael Noonan, said the killing of Mr Brett was an "appalling tragedy which struck at the heart of peace and reconciliation".
Mr Noonan added: "If young Catholics and Protestants in Northern Ireland cannot begin to socialise in a normal peaceful way . . . then the North is facing a long period of [being] a seriously dysfunctional society."