Russian President Boris Yeltsin and Moscow Mayor Yuri Luzhkov have apparently put aside their rivalries - temporarily at least - to face up to the most serious threat yet to post-Soviet Russia's stability.

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But even if Russia's authorities do unite to combat the threat of more bombings of residential buildings, it is a huge challenge.

International experience has shown that even when the most stringent measures are applied, the cleverest minds put to work and huge numbers of people put on guard, it is virtually impossible - in the short term - to prevent all acts of political terror.

Most experts agree that the only final solution to what is widely called 'terrorism' is the long-term political one - in other words to eradicate the grievances which have provoked such horrific acts.

But since political solutions can take years, indeed decades, governments also have to take short-term preventative measures - and this is what Russia now has to take.

Retaliation

It is impossible to prevent all acts of terror but it is possible to cut them down to a minimum.

Security forces in different parts of the world use different approaches. Israel, for example, has resorted to retaliation against Palestinian targets for the attacks on its military and its civilian population - and this retaliation has in some cases involved targets like refugee camps which inevitably caused civilian casualties.

This is not an approach universally accepted. Its critics argue that it merely prolongs bitterness and conflict - quite apart from the lack of concern with civilian casualties.

So what is left? The alternative is, even in cases where there is widespread public outrage against the people of violence, to limit the security forces to measures of control and restraint, and to concentrate on detection.

Rather than target whole groups or a wide range of suspects, this method requires hard work to find hard evidence on the real culprits.

If whole groups of citizens are victimised, this can worsen the problem rather than cure it.

The UK learned this lesson early on in Northern Ireland, when wide-ranging arrests of people 'suspected' - sometimes on flimsy evidence - of being Irish Republican activists merely embittered the Catholic population and actually increased the ranks of the activists.

Long-term approaches

Sometimes, however, detection can take a lot of time, involving painstaking accumulation of evidence and infiltration of the extremists' ranks.

While this is taking place the security forces have to mount guard on as many potential targets as is possible.

It can be a huge and costly operation, and requires lots of stoicism from the public, and responsibility and restraint from politicians and soldiers.