The two 12-year-olds and a two-year-old suffered minor injuries when a device exploded in a bin in Lurgan, Co Armagh. The attack was said to have been an attempt to target police officers and came as the focus was on a major loyal order parade in Londonderry.
The first half of the Apprentice Boys of Derry parade took place without major incident after a protest by dissident republicans was cancelled. The parade, involving an estimated 15,000 people and a large number of bands, is returning through Derry. It passed through the flashpoint Diamond area without major incident.
But in Lurgan politicians blamed dissidents for the bomb attack and said disaster was narrowly averted when the three children suffered minor injuries from flying debris when there was an explosion in a wheelie bin.
Chief Inspector Sam Cordner said: "This no-warning explosion occurred in North Street in Lurgan and was an obvious attempt to kill police or injure police officers ....as they responded to a neighbouring area following a very vague warning that a device had been left at a local school. It is an absolute miracle that these children were not more seriously injured."
Police and bomb disposal experts examining suspicious objects in the Lurgan area have come under petrol bomb attack. There were no reports of injuries.
Meanwhile, police in Derry said they had arrested a number of people for disorderly behaviour during the first half of the Apprentice Boys parade.
Nationalists staged a silent protest at a parade linked to the Derry march in the Ardoyne area of north Belfast, where there was rioting after an Orange Order parade last month. It passed off without incident.
Earlier, there were scuffles between police and nationalists at Ferryquay Street in Derry after a small crowd had exchanged taunts with supporters of the Apprentice Boys parade.
In a further development, police in Derry have charged a second man in connection with a car bomb attack on Strand Road police station in the city last week. The 53-year-old will appear at Derry's magistrates' court on Monday to face a series of charges, including alleged weapons offences.