Four Afghan Army units that had been guarding the capital city of Kabul have been moved into the countryside and replaced by Soviet forces, Western diplomats reported here today.

The reported transfer of responsibility for guarding Kabul, which is going through a rash of lawlessness and killings, signaled a major shift in Moscow's strategy for taming the fiercely independent Afghans resisting the 15-month occupation of their nation, diplomats said.

According to one analyst here, the shift indicates that the Soviets no longer trust the Afghan Army units to guard the capital even under the supervision of Soviet troops.

Indicating lack of trust, Soviet armored vehicles spread through the city Monday night, taking positions in a broad perimeter that encircled the Soviet VIP guest house where the chairman of the Soviet State Committee for Foreign Economic Relations, Semen Azndreyevich Skachkov, was staying.

The shift in responsibility for guarding Kabul was reported to have come yesterday, when the four Army divisions in the city -- once Afghanistan's crack units -- began moving out of the city.

They are reportedly being sent to the provinces to fight. But military analysts believe it is unlikely that they will be successful battling the rebels since these divisions, along with the rest of the Afghan Army, are plagued by desertions of officers and men.

Moreover, there have been repeated reports of plots by officers of the four divisions -- the 4th and 15th Armored and the 7th and 8th Infantry -- against the Soviet-installed government of Babrak Karmal.

Meanwhile, according to diplomatic sources here, a winter lull in fighting between Soviet and Afghan forces and the rebels is ending. There are reports of fresh eruptions of fighting in 20 of Afghanistan's 29 provinces, including all nine that run along the Soviet-Afghan frontier.

Other reports reaching here described attacks on Soviet and Afghan installations in Herat, a city near where the Afghan, Iranian and Soviet borders meet. The attacks, according to diplomats here, were part of the celebration of the second anniversary of the Herat uprising, in which Soviet civilians and soldiers were mutilated and killed by Afghan rebels.

Three of the four major highways leading out of Kabul were reported closed most of the past week because of heavy fighting. There were also reports of Soviet jet and helicopter attacks on Torgundi, a border post north of Herat where an uprising is supposed to have taken place.

In Kabul itself, there have been numerous reports of violent incidents including the daylight shooting Sunday by soldiers of a man outside of movie house in one of the capital city's more well-to-do neighborhoods.

There are also rumors circulating in Kabul that Mohammed Amin Sadr, who is known as the government's leading supporter among the Islamic clergy, was shot and killed in the center of Kabul on Friday.