Amid the celebrations, it is never wise to forget Northern Ireland

Much of the country has spent the past three days cheerfully wrapped in one flag or other, enjoying the first flush of warm weather, the spectacle of the Queen's jubilee celebrations, or a breakfast-time pint while viewing the World Cup. One corner of the realm, however, has remained stubbornly undiverted by such pleasures. The Short Strand area of east Belfast has witnessed the shooting of three people and some of the fiercest sectarian clashes of recent years.

Much of the country has spent the past three days cheerfully wrapped in one flag or other, enjoying the first flush of warm weather, the spectacle of the Queen's jubilee celebrations, or a breakfast-time pint while viewing the World Cup. One corner of the realm, however, has remained stubbornly undiverted by such pleasures. The Short Strand area of east Belfast has witnessed the shooting of three people and some of the fiercest sectarian clashes of recent years.

That a trio of non-fatal shootings and strictly localised rioting should have hit the national headlines is, in a perverse way, a consolation of a sort. Sectarian killings in Northern Ireland are now rare; bombings – still rarer. Violence, while still pervasive, is at a much lower level than before. Yet the latest upsurge in rioting, apparently sparked by members of the Protestant majority hanging up jubilee bunting, is a salutary reminder that not all is as peaceful and contented as it might appear from Britain – nor is everyone as loyal to, or tolerant of, the Crown.

Short Strand, a small Catholic enclave surrounded by Protestants, has long been a barometer of tension in the province. It exploded in the Twenties, in the Seventies, and now threatens to do so once again. In such an area, hanging out bunting will always be interpreted as marking out territory rather than an expression of innocent celebration, and those who display it are as aware of that reality as those who object to it. Flags are flags, whatever their shape or size.

As ill-luck would have it, the jubilee weekend coincides with the early weeks of the Northern Ireland marching season, an incendiary time when even the flimsiest of symbols can revive the most dormant of flames. Low-level rioting has broken out on several recent nights in north Belfast and in the west of the city. So far, however, the clashes have remained localised in cause and effect.

The risk is that the shootings in Short Strand precipitate more generalised violence. Which is why it is crucial that, if they do not abate, the clashes here at least remain geographically confined. It is also why the province's acting Chief Constable, Colin Cramphorn, warned that Northern Ireland as a whole could be heading for "a fresh nightmare" and risked "sleepwalking into an abyss" unless both sides stepped back from the fray.

The necessary, but controversial, restructuring of the Northern Ireland police force only adds to the perilous mix. Low morale, high absenteeism and internal friction all threaten to diminish the force's capability at the very time when discipline, strength and forbearance are most needed. As the acting Chief Constable also warned yesterday, the police, like the British army before them, have become the buffer between the two sides and thus the object of hatred even as they do their best to preserve life.

With this year's marching season still so young and nightly violence already setting in, the auguries for a peaceful summer are not good. If the considerable gains in Northern Ireland are not to be squandered, it is vital that political and religious leaders of both communities add their voices of warning to Mr Cramphorn's and apply all their persuasive skills to defusing the tension – before the security situation becomes irrevocably worse.