The commander of the U.S. military liaison mission in East Germany was injured last Saturday when his car was rammed from behind by a Soviet military truck, U.S. Army officials said today.

The incident was the third in four months involving Soviet action against American and British military liaison teams in East Germany.

The U.S. military command in Europe has registered a protest with Soviet forces in East Germany over the collision, which occurred near Satzkorn, northeast of Berlin, in the early hours of Saturday.

It was the first altercation between Soviet troops and the American military liaison unit since March when a Soviet sentry shot and killed Maj. Arthur D. Nicholson, a member of the 14-man team.

The driver of the vehicle involved in the latest episode, Army Staff Sgt. Jessie Schatz, was also behind the wheel of the car on the mission when Nicholson was killed.

The 380,000 Soviet forces based in East Germany are now carrying out a major military exercise called Soyuz-85, and it is believed that western -- U.S., British and French -- liaison teams have been coordinating their daily patrols to glean as much information as possible about the latest weaponry and military tactics being deployed by Soviet troops.

Col. Roland Lajoie, the head of the U.S. liaison group, suffered facial fractures in the accident, according to Pentagon officials. Lajoie was one of three passengers in the American vehicle.

The Americans, who were not armed, were said to be observing Soviet troops returning to their base on a highway in an unrestricted area, when their car was rammed from the rear by what was described as a five-ton Soviet truck.

In Washington, Pentagon spokesman Fred S. Hoffman said the truck, carrying at least two Soviet soldiers turned on its high beams as it approached the U.S. vehicle, which was clearly marked with a license plate identifying it as belonging to the liaison team. After speeding up, the U.S. vehicle pulled off the road to turn around and was rammed, he said.

[Hoffman said the Pentagon views the matter "very seriously." He said the incident underlines the "difficulties that our perfectly legitimate liaison teams have been experiencing in East Germany, where we're entitled to be."]

U.S. military and diplomatic sources said they were still awaiting a full account of the collision and the circumstances surrounding it.

On June 4, three officers belonging to the British liaison group were harassed for five hours by Soviet soldiers, who hurled bricks and waved cocked weapons at them after ramming their car with a truck.

The recent violent incidents in the wake of Nicholson's death have raised fresh doubts about the status of the ground rules governing the activities of the liaison units established by the four wartime Allied powers after World War II.

A certain amount of jostling and harassment is considered part of the game, intelligence sources say. Soviet or East German Army vehicles have been known to bump or ram western military cars if they stray too close to sensitive installations. Soviet soldiers have fired warning shots at western officers on several occasions in the past, and a French liaison member was killed last year when his car was struck head-on by an East German truck.

Shortly after the Nicholson shooting, the acting commanders of U.S. and Soviet forces based in West and East Germany -- Gen. Glenn Otis for the United States and Gen. Mikhail Zaitsev for the Soviets -- met and reportedly reached agreement not to permit "use of force or weapons" by their soldiers in controlling the movements of the liaison groups, who conduct what is tantamount to sanctioned espionage in the former occupation zones.

The Soviet armed forces newspaper Red Star has carried two unusually critical articles in recent months about the poor condition, training lapses and lack of discipline among Soviet troops in East Germany.

Zaitsev was relieved of his duties last week. His departure was announced along with that of his deputy, Gen. Alexei Lissichev, by the official East German news agency on Saturday. Their successors have not been named yet.

Western military experts expressed surprise at their sudden removal, but there were no clear indications whether the two Soviet generals went home in disgrace. East German leader Eric Honecker publicly thanked both of them "for their services in strengthening the defense of socialism."

Zaitsev has long been regarded as a powerful military figure and a possible successor to Marshal Viktor Kulikov, the supreme commander of all Warsaw Pact forces.

During Zaitsev's meeting in April with Otis, the Soviets refused to yield to other U.S. demands at the meeting, including a formal apology for the shooting and compensation for Nicholson's family. Moscow said it regretted the U.S. major's death but still defended the actions of the sentry, who allegedly fired after Nicholson refused to heed several appeals to halt.

The Soviets claimed the 37-year-old Russian-speaking American was taking photographs within a restricted military area near Ludwigslust, but the United States still contends that Nicholson was several hundred yards outside the proscribed zone.

Diplomats say the daily reconnaissance sorties by the liaison missions are generally conducted by teams of two to four members, who pick up what is judged to be some of the best ground intelligence to be found along the Central European front.

Their marked military vehicles, equipped with infrared cameras, listening devices and binoculars, roam in search of hard information on the nature and location of troops, missiles and armor.

Only designated military areas are considered forbidden territory to the roving liaison members, who still are known to bend their restrictions. As much as 40 percent of East Germany is now said to be off-limits to western teams, and some of the problems they have encountered are said to be rooted in Soviet fears that they are picking up too much security-related data on their rounds.

The United States and the Soviet Union signed the accord in 1947 giving each side an outpost and travel rights in the other's occupation zone in Germany and the right to accredit 14 officers and enlisted men to their missions. The Soviets signed similar pacts with France and Britain.