RECENT incidents along the northern end of the Pakistan-Afghan border amount to nothing less than a low-intensity war. Groups of up to several hundred militants have carried out attacks against anti-Taliban militias and Pakistani security forces in Mohmand and Bajaur agencies and Dir in the last three months. Both the Pakistan military and experts say the militants are crossing over from Afghanistan, especially Kunar province, which Nato troops have withdrawn from in the last six to eight months. This week saw a serious intensification of the conflict: several hundred fighters attacked villages in another incursion into Upper Dir on Wednesday, and in a reversal of the trend, the northern Afghan province of Nuristan saw an intense clash that the provincial governor claimed had been launched by militants from Pakistan.

The prevailing theory seems to be that the fighters crossing into Pakistan are those driven out by military operations in Swat and Fata who sought refuge in Afghanistan. Experts also argue, however, that it is futile to try to separate the roles of the Afghan and Pakistani Taliban in these instances. Sanctuaries imply local support, and the border runs through, rather than between, tribes in these areas. The reverse attack into Afghanistan this week also points to the easy cross-border movement of militants with different targets and agendas that are not yet clear.

Given these realities, the need is for the Pakistani and Afghan governments to recognise their shared responsibility and agree on concrete measures to be taken on both sides of the border. Pakistan continues to lodge protests with Kabul over the attacks and the latter has accused Pakistan of firing hundreds of rockets into its northern border regions. Although the military has denied these were aimed at Afghanistan, even Pakistani observers say they were likely targeted at militants taking cover there. Whatever the case, the Afghan government and Nato must recognise that they need to take steps against sanctuaries in Afghanistan if they expect Pakistan not to do so. Kunar and its neighbouring provinces may be remote, sparsely populated and of relatively limited strategic value for Afghanistan, but it is the Afghan government's responsibility to dismantle sanctuaries from which Pakistan is being attacked. In return, however, Pakistan should offer to do the same on this side of the border to the extent it is possible to do so without sending militants fleeing next door. Continued rocket fire could hamper the crucial relationship between Afghanistan, Pakistan and the US, but Afghanistan's approach of condemning without taking action will do little to tackle a new theatre of war that is spiralling out of control.