The Nato air strike on the Bab al-Aziziya compound in Tripoli, which has apparently resulted in the deaths of civilians, looks like a grave mistake. Lieutenant General Charles Bouchard, the Canadian commander who authorised the attack, has claimed that the compound was a "known command-and-control building" for the Gaddafi regime. And the British Foreign Office minister Alistair Burt has pointed out that Libyan military command centres are often placed in civilian areas. But that is precisely why these aerial attacks are usually a bad idea. The odds of success are so low and the chances of killing innocent civilians so high.

The Libyan regime claims that Gaddafi's 29-year-old son, Saif al-Arab, and three of the leader's grandchildren were killed in the bombing. There has been no independent confirmation of that. But the episode has already turned into something of a propaganda victory for Gaddafi. Aerial bombing, particularly when it goes wrong, tends to rally populations in anger. We saw evidence of that taking effect in Tripoli yesterday, when United Nations buildings and foreign missions, including the British Embassy, were attacked by crowds.

Last week the US Defence Secretary, Robert Gates, and our own Defence Secretary, Liam Fox, told reporters in Washington that Nato was not directly targeting Gaddafi in these air strikes. Yet this bombing certainly resembles an attempted targeted assassination. It is unlikely to be a coincidence that Gaddafi himself is reported to have been in the compound at the time of the attack, although he is said to have been unharmed.

We have been here before. US air strikes on Tripoli in 1986, in response to suspected Libyan involvement in the bombing of a Berlin disco, killed Gaddafi's adopted daughter. Lessons do not appear to have been learnt. That episode enabled Gaddafi to shore up his position, presenting himself as a defender of Libya against foreign aggression.

Yesterday, David Cameron claimed justification for the strike under United Nations Resolution 1973, which allowed "all necessary measures" in order to protect civilians in Libya. There is, admittedly, room for debate about the resolution's meaning. But to find a justification for targeted assassinations in it is too much of a stretch.

The diplomatic strain is growing. International support for this operation is already threadbare. Russia and China are now opposed. Their antipathy will be hardened by this botched raid. Targeted assassinations even risk splitting Nato. Germany and Turkey are likely to be further alienated from the mission now.

But the real error is strategic. These strikes give the impression that the operation is, at heart, a confrontation between Gaddafi and the West. They leave the Libyan opposition looking helpless on the sidelines. That turns an internal revolt against a vicious dictator into another Western military adventure.

After six weeks of bombing, the situation in Libya looks like stalemate. Gaddafi's regime has proved resilient and his forces loyal. Advisers from France, Italy and Britain have been sent to assist the opposition and the US has dispatched unmanned drones. This was initially interpreted as an escalation in the foreign commitment. But some observers regard it more as a way of compensating for the fall in bombing since the US handed over the lead to Nato. In this context, the bombing of the compound begins to look like an act born of desperation; a desire to force a quick resolution before partition becomes inevitable.

Yet this is the Libyan opposition's fight, not Nato's. If the rebels are to achieve their objective of removing Gaddafi and uniting the country, they have to be seen to be leading the resistance. Nato does them, or indeed itself, no favours by trying to force the pace.