It could so easily have been the worst sporting atrocity since the 1972 Munich Olympics. The fact that yesterday's military-style ambush of the Sri Lankan cricket team did not lead to greater loss of life seems attributable to the quick thinking of their bus driver and sheer good fortune.
But as an act designed to spread terror, the attack will surely be effective enough to satisfy those who ordered it. There will be no international sporting fixtures in Pakistan for the foreseeable future. The attack might even result in teams staying away from the wider South Asian region. Last November's terror attack in Mumbai drained confidence; Lahore could destroy it entirely.
But the ramifications of this attack go far beyond sport. It is another sign of the extreme instability of the Pakistani state. The reach of the country's sprawling Islamist insurgency, one of the branches of which was probably responsible for yesterday's attack, appears to be growing. The bombing of the Marriot Hotel in Islamabad last September showed that not even Pakistan's capital was secure. And the government now concedes that the devastating Mumbai attacks were planned and directed on Pakistani territory.
Leaders of the Punjabi-based Lashkar-e- Toiba (LeT) group were arrested after the Mumbai outrage. Yet LeT is one of several militant factions that were trained and resourced by the Pakistani intelligence services to mount attacks against the Indian army in Kashmir in the 1980s. Many independent analysts believe that such support continues in secret.
There are few signs of progress in Islamabad's struggle to defeat militants in Pakistan's north-western regions either. The government did a deal last month with the tribes of the Swat Valley allowing them to entrench sharia law in exchange for a truce. Islamabad has portrayed the arrangement as a device to separate the religious conservatives of the region from the militants. To the outside world, however, it looks more like a capitulation to extremism – and one that will merely make the task of defeating the Afghan Taliban, who find safe haven in Pakistan's tribal regions, more difficult.
Making matters worse, the civilian government that replaced the military regime of General Pervez Musharraf last year is weak and compromised. President Asif Zardari seems to be devoting more attention to thwarting his political rival, Nawaz Sharif, than suppressing the insurgency.
The outside world has been stepping up pressure on Islamabad to weed out those elements in its intelligence services that still protect insurgent "clients". This is necessary, but not without risks. Apply too heavy a hand and there is a danger of undermining the civilian government and boosting the extremists. Anti-US resentment is already growing, stoked by sporadic US air raids across the Afghan border. Taking the fight to the terror groups, while supporting Pakistan's civilian government, will not be easy.
Yet the outlook is not entirely bleak. Despite the proven reach of the extremists, most Pakistanis are religious moderates. Islamist parties did poorly in last year's elections. Nor is there any appetite for a return to army rule.
The best international response to yesterday's vile attack in Lahore is a firm message of support for the moderate forces in Pakistani society – and a determination to encourage the spread of democracy and law into every corner of this turbulent state.