Hundreds of Soviet-built tanks and waves of Mig jet fighters blasted the presidential palace and key government buildings in Kabul during this week's bloody coup in Afghanistan, eyewitnesses reaching this border checkpoint reported yesterday.

The accounts of the fighting, in which hundreds of persons were killed or injured, came from five Western tourists, including two Americans, who were the first to emerge from Afghanistan since Thursday's coup.

The new military regime announced over Kabul Radio that 200 persons had been killed in the coup. The broadcast said that in addition to President Mohammed Daoud, whose death had been reported earlier, the vice president, the ministers of defense and interior, and the air force commander also were killed.

Eyewitness accounts spoke of hundreds if not thousands of casualties.

"I never knew the Afghan army had so many tanks," said Jan Bubela, of Dallas. "They were everywhere, hundreds and hundreds of them, and many of them had been knocked out in the battles. It was all very fierce stuff."

Ben Swelderns, a Dutch architect, said the coup began before 11 a.m. Thursday when soldiers with rocket launchers and rifles took up positions on Kabul streets, and tanks moved into key city squares and in front of the presidential palace.

"But nothing happened until midday, exactly," Swelderns said. "It had obviously been planned for that very moment. As soon as the clocks struck twelve, the tanks let go with huge blasts of fire, all directed at the palace.

"They got into a routine: five minutes of shelling than ten minutes of quiet, then another five minutes of firing and so on. Than at about 3 p.m. fighter bombers started sweeping across the town, swooping down low over the palace and one or two other places and letting off their rockets in great clouds of smoke."

Irmgard Lohren, of New York City, a TWA stewardess, said the presidential palace "was very badly knocked about. The tower was knocked down and the presidential flag was at half mast" when she toured the city Friday.

"The big Ariana hotel in the middle of town was burned and all its windows were knocked out," she said. "It must have been from the tanks. They were shelling almost without pause during the late evening, and the noise and the vibration were incredible."

Among other buildings damaged by rocket fire were the military command headquarters and a police training center, the witnesses said. Huge fires burned inside the compounds of these buildings.

The western tourists came out of Afghanistan as the new government yesterday allowed the first legal light traffic across the border to Pakistan. Kabul's airport remained closed to incoming traffic, however.

Kabul Radio programming was nterrupted occasionally with appeals from the new military junta for calm and for the rooting out of what it called "anti-revolutionary elements."

Diplocatic sources reported that armored vehicles were patrolling Kabul streets and that civilians were directing what little traffic was on the highways. This tends to confirm earlier suggestions that many police were casualties during the initial stages of the coup.

The five Western travelers arrived at the Khyber Pass checkpoint on the Afghan-Pakistan border shortly before sunset, when the border closes. They described the 150 mile journey from Kabul as difficult.

Army checkpoints every five miles, manned by "extremely nervous young soldiers," forced the five travelers to take more than 10 hours for a trip that normally takes three hours . . .

Kabul Radio said last night that the new Military Revolutionary Council is in complete control of the mountainous country, a largely agricultural land of 20 million that borders on the Soviet Union, Iran and Pakistan.

The head of the council was identified as Col. Aslam Watanjar.

In their broadcasts, the new rulers said Afghanistan will remain "democratic, Islamic, reformist and nonaligned" and that it would honor its "international commitments and will respect its neighbors and the honorable and respectful religion of Islam."

Continuing a 10 p.m. curfew, the council announced that "the holding of every kind of assembly is banned" but that "the people should pursue their normal work and life."

According to diplomatic reports, the new government has made no direct contacts with Western embassies in Kabul.