The salvo of cluster rockets, which scatter bomblets over a wide area, landed in mid-afternoon on Khair Kana, an outlying northern district to which hundreds of thousands have fled during the latest outbreak of fighting among Afghanistan's myriad factions. A large crowd of displaced people had gathered outside the Abu Muslim mosque, where a private aid organisation, CARE International, was distributing two truckloads of wheat flour brought in by a United Nations convoy at the weekend.
Several survivors blamed the attack on Gulbuddin Hekmatyar, whose forces have been besieging Kabul since January. Although the city is constantly under fire, cluster rockets are rarely used and they believed the Hizbe Islami leader might have been seeking to disrupt the food handout. Since the beginning of February Mr Hekmatyar has been preventing food reaching the capital in an apparent attempt to increase the pressure on President Burhanuddin Rabbani to resign.
He seized the UN convoy last Thursday and only allowed half its cargo - three trucks - to cross into the government-held area after what he said was a personal appeal from the UN Secretary-General, Boutros Boutros-Ghali.
If Mr Hekmatyar was trying to discredit the UN, yesterday's events certainly played into his hands. The scene at Khair Kana had been peaceful earlier in the day. According to the CARE supervisor, Abdul Majid, this was because he had managed to eke out three truckloads received before the blockade took hold.
At Karte Parwan, however, a wealthier area, no food had been distributed for weeks and a near-riot broke out when the third truck was sent there. News that food had arrived brought several hundred people to the CARE depot, and a thin line of mujahedin was swept away as they burst into the yard where the sacks had been piled up. One man fired a burst into the air without effect, and the supervisor, Ayoub Maftoun, was mobbed. After half an hour of chaos, he announced that no flour would be distributed until the next day, but this failed to disperse most of the crowd.
In the afternoon, as Kabul's opposing forces resumed their bombardment of each other's mountaintop positions, Mr Maftoun gave up. The system of ration cards was abandoned, and women were formed into groups of 10 to receive one sack each.
Several people among the mainly middle-class crowd bitterly criticised the UN for failing to impose peace. One even blamed Britain: Gulam Nabi, whose brother was a minister in the former Communist regime, claimed the British 'haven't forgotten the three defeats they suffered in Afghanistan' and were discouraging any UN action. Mr Nabi had been driven out of Mikrorayon, a Soviet-built housing estate for Communist loyalists. The Uzbek militia of Abdul Rashid Dostam, who precipitated the renewed struggle for power by switching to Mr Hekmatyar's side, took the chance to loot and burn the apartment blocks. 'Last week I sold my last carpet,' he said. 'Now I have nothing left to sell.'
Although the anti-government alliance is unlikely to starve Kabul into submission - plenty of food has been smuggled in, even if the number who can afford it is shrinking - the blockade adds to the misery of a city whose heart has been torn out. More than 1,000 have been killed and 12,000 injured since fighting began on New Year's Day.