KABUL, Afghanistan -- A truck bomb exploded in crowded downtown Kabul today, killing six people and wounding 49 on the final day of celebrations marking the 1978 coup that brought the ruling party to power.
Brig. Gen. Saifullah, in charge of police in the Kabul area, said the truck had Pakistani license plates and he blamed the blast on U.S.-backed Moslem rebels fighting to topple the Soviet-installed government. He said terrorists timed the explosion to coincide with the 10th anniversary celebrations.
Radio Moscow blamed the blast on 'opponents of the people's government' who want to frustrate the Afghan peace pact signed recently in Geneva and opposed by the Afghan guerrillas.
No group claimed responsibility for the explosion, which echoed across the basin in which Kabul sits when it occurred about 12:30 p.m. near the Pamir movie theater as crowds thronged nearby markets. A gray pall of smoke covered the area.
The force of the blast destroyed the truck and hurled its tangled wreckage off the side of the road, down an escarpment and on to the bank of the Kabul River, which flows through the heart of the city.
Windows of nearby buildings were shattered and several vehicles standing nearby were badly damaged. Shards of glass and pieces of metal littered the street and the spot where the truck had stood was scorched black.
Scores of plainclothes and uniformed police and paramilitary troops cordoned off the area.
Saifullah told reporters six people -- four men, a woman and a girl - were killed in the blast and 49 were injured, 27 of them hospitalized. He said a time-bomb was planted on the truck and he produced a Pakistani license plate he said was on the vehicle.
Tass, in a three-sentence dispatch issued several hours after the explosion, reported Afghan investigators said the truck arrived in Kabul from Pakistan, an Afghan guerrilla base of operations.
'Investigating authorities said the truck, which arrived in Kabul from Pakistan, must have carried an estimated 150 or so kilograms of explosives,' Tass said in its dispatch from Kabul released in Moscow.
Initially, this reporter and a Japanese photographer, the first foreign journalists to arrive on the scene, saw rescue workers carrying three bloodied bodies of men into waiting ambulances.
The two journalists were seized by paramilitary troops while taking photographs and the film was ripped from the photographer's camera. The pair were taken to a police station and questioned for 90 minutes before being released.
Police said they seized the journalists because they were not carrying passports. Their passports were taken Tuesday by government officials for visa renewal.
The last known bomb attack to hit Kabul was March 27 when a jeep packed with explosives blew up, killing five people, including four Soviet advisers, according to Western diplomats.
Western diplomats have blamed a spate of car-bombings this year in the Afghan capital on Moslem rebels and in-fighting between factions of the ruling Peoples Democratic Party of Afghanistan.
Today's explosion came on the final day of celebrations of the anniversary of the April 27, 1978, military coup that brought the PDPA to power.
Gulbuddin Hekmatyar, leader of a seven-party Afghan guerrilla alliance, said Tuesday the rebels planned to disrupt the anniversary celebrations and the results would be known in 'the next day or so.'
Massive security measures were imposed across the city for the celebrations. But the bombing appeared to confirm the vulnerability of the Afghan capital, which is expected to increase considerably following the pullout of an estimated 115,000 Soviet troops beginning May 15.
The Soviet Union invaded Afghanistan in December 1979 to stabilize the PDPA government, which was beset by serious internal feuds and a rebellion by Moslem tribesmen across the landlocked nation.
But even with the support of the Red Army and the Soviet air force, the 40,000-man Afghan army has been losing ground to the rebels who are armed by the United States, China, Iran and Arab nations and are based mainly in neighboring Pakistan.
The Soviet Union agreed to withdraw its forces within nine months under U.N.-mediated accords signed in Geneva April 14 between it, Afghanistan, Pakistan and the United States.
The bombing came several hours after President Najibullah, members of his government and guests attended a youth festival, one of several events to mark the 1978 coup.
In Peshawar, Pakistan, Hekmatyar marked the anniversary by telling reporters Tuesday that the resistance would fight Soviet troops 'until the last Soviet soldier leaves Afghanistan.'
'The coup has brought us tears, pain, fire and bloodshed,' Hekmatyar said. 'It has resulted from the friendship of our past governments with the Soviets. The Soviets are responsible for the bloodshed.'
The resistance, which Western diplomats say controls most areas of the country, rejected the accord and vowed to continue its fight for an Islamic government.
In Islamabad, Pakistan, Western diplomats said Soviet forces have begun pulling back from Afghan provinces on the Pakistani border and consolidating in preparation for the start of the withdrawal.
In another development, Afghan army units shelled across the border into Pakistan for the second consecutive day Tuesday, killing two people, wounding eight others and destroying several houses in the village of Ghakhi, 120 miles north of the frontier town of Peshawar, local officials said.