Leading article: Al-Qa'ida's waning influence

The twin bomb attacks on a paramilitary academy in Pakistan yesterday were followed by a boast from the country's Taliban that the purpose was to avenge the killing of Osama bin Laden. As such, the assault can be seen as a warning for the future and the first real evidence that forces loyal to Bin Laden are still in business. Yet it would be wrong to rush to too many conclusions.

Simultaneous suicide bombings have often been seen as tantamount to a trademark of al-Qa'ida, which would reinforce the idea that Pakistan's Taliban, like its Afghan counterpart, are in league with al-Qa'ida. So well-known has this trademark become, though, that it may no longer be an authentic signature. At the same time, there may be those keen to capitalise on Bin Laden's notoriety by claiming an association they do not have.

An attack on an academy that trains border guards might also seem a rather oblique way of avenging Bin Laden's death. So, was the prime purpose vengeance, or was it rather to vent anger that Pakistan had been unable or unwilling to keep Bin Laden safe?

It is worth observing, too, with fingers tightly crossed, that this is the first attack to claim a link with Bin Laden since the al-Qa'ida leader was killed almost two weeks ago. Whether for lack of organisation, or funds, or will, there was no immediate spate of retaliatory bombings. And when this one came, it was inside Pakistan in a region that might almost be described as local.

This is no reason, of course, to relax the state of vigilance that many governments introduced after President Obama announced the demise of America's Enemy No 1. Indeed, it could well be argued to the contrary. Depending on what happens in coming weeks, however, the scale, timing, location and nature of yesterday's attacks could be seen as signs that al-Qa'ida's influence is on the wane, as the conspicuous absence of its name from the current ferment in many Muslim countries already suggests.