Marching season in Northern Ireland once again has fanned the flames of sectarian violence. The police are currently investigating a firebomb attack that killed three young boys over the weekend. Following a background report, the Irish and British ambassadors to the United States discuss the recent violence.

JIM LEHRER: Northern Ireland's story and to Margaret Warner.

MARGARET WARNER: Church bells called mourners to another funeral in Northern Ireland today--which has seen more than 3,000 for victims of sectarian violence over the past three decades. Friends and neighbors wept as the caskets of three young Catholic brothers, one carried by the father of one of the boys, were born into the parish church in the rural town of Ballymoney, 40 miles northwest of Belfast.

The three Quinn brothers--Richard, 10; Mark, 9; and Jason, 7-were killed early Sunday morning when a Molotov cocktail was hurled into the home where they lived with their mother, a Catholic, and her Protestant boyfriend. Parish priest Peter Forde addressed the mourners--Catholics and Protestants--who had assembled inside and outside the church.

FATHER PETER FORDE: This weekend in the wake of horrific martyrs of the three young children voices have been raised, voices of sanity, voice of reason. Words of healing have been spoken.

MARGARET WARNER: The boys were buried in a single grave in their grandmother's village, Rasharkin, seven miles away. Sunday's firebombing culminated a week of rising tension in Northern Ireland triggered by the onset of the Protestants' annual marching season commemorating Protestant victories over Catholics in centuries past. Violence flared after local police and British soldiers blocked a July 5th march by the Protestant Orange Order through a Catholic neighborhood in the town of Portadown, southwest of Belfast.

An independent parades commission had banned the march down the Garvaghy Road, whose Catholic residents violently opposed it. Thousands of angry Orangemen and Protestant sympathizers camped out around the Drumcree Church at the head of the parade route. They hurled rocks and gas bombs at the security forces, and vowed to stay until they could complete their march. After the firebombing, the first minister of the newly-elected Northern Ireland assembly, Protestant Leader David Trimble, himself an Orangeman, said it was time for the Protestants and Orangemen to go home.

DAVID TRIMBLE: I must say to the Portadown residents that the only way in which they can clearly distance themselves from these murders, show to the world that they repudiate those who have murdered young children and use that as an excuse for that, the only way they can repudiate that is not only to leave the hill at Drumcree Parish Church and return home.

MARGARET WARNER: Yesterday, several hundred parades previously approved by the commission went forward -- but in subdued fashion. On one controversial route, down the lower Ormeau Road in Belfast, the Protestant Orangemen marched, but muted their band as the parade commission had ordered. Catholic residents, who had vowed to resist the march, instead stood silently, holding black flags. Back at Drumcree, new skirmishes broke out between Protestants and police. But the number of demonstrators had shrunk from thousands last week to fewer than 200 last night.