Loyalists last night threw two bombs at a community theatre staging a children's play as part of a community festival in the Ardoyne area of north Belfast.
The Northern Secretary, John Reid, is meeting the RUC chief constable, Ronnie Flanagan, later today to discuss the worsening security situation.
The devices were blast bombs, packed with nails and shrapnel.
The Red Hand Defenders, a cover name for the UDA, said it was responsible.
Earlier the same group, used in the past as a cover name for the Ulster Defence Association and the Loyalist Volunteer Force, said it carried out the killing of Protestant teenager Gavin Brett, gunned down as he stood with friends on the Hightown Road on the outskirts of north Belfast.
Meanwhile, the RUC used water cannon to disperse a loyalist crowd which launched an attack on nationalist homes in north Belfast.
A crowd of more than 100 Protestants from the Gunnell Hill area threw missiles at houses belonging to Catholics.
However, community worker Brian Dunn of the Whitewell Residents Group says the trouble began when Protestants' houses were stoned. Earlier, riot police had been sent to the area after clashes between rival factions.
Both sides blamed each other for the sporadic violence. Nationalists claimed homes were attacked in the Longlands area while loyalists insist their houses first came under attack.