Elements of the 82nd Airborne Division were put on alert yerterday amidst mounting fears for the safety of foreigners, including Americans, caught in the war zone around Zaire's southern mining town of Kolwezi.

As heavy fighting between pro-government troops and the rebels continued for the sixth day around the country's most important copper center, reports in Lusaka, Zambia, said that three or four Europeans had been executed over the weekend.

The Zambian reports also said about 15 Americans were being held by rebels, although State Department officials in Washington said they had no information about American captives.

The Pentagon would not disclose how many troops or aircraft had been put on alert at Pope Air Force Base in North Carolina, But Military sources stressed that the force would be used for evacuation only and not to go to war in Zaire.

It was the first time troops had been alerted in an overseas crisis in the Carter presidency.

The alert stemmed from Carter administration worries about 75 Americans living near Kolwezi, where fighting has been heavy, officials said.

Sixty-two of those Americans are employees of the Morrison-Knudsen construction firm, which is building a power facility in Kolwezi. The other Americans are nine missionaries, one employee of a copper firm and one tourist.

"We are very much concerned about this renewal of conflict in the Shaba area" of Zaire, State Department spokesman Hodding Carter said yesterday.

"Our first concern is the welfare of Americans," Carter said, adding that "to the best of our knowledge" there have been no American casualties in the war in Zaire, although one child had been reported injured.

Secretary of State Cyprus Vance, in a separate meeting later in the day with Congressional leaders, called the military situation in Zaire "somewhat confused," and said evacuation of Americans "may be necessary."

The 82 Airborne is structured to fly to trouble sport like Zaire on short notice, usually one battalion about 800 men at a time. The paratroopers land equipped to fight.

The Pentagon said last night that no other military units, such as warships, had been placed on special alert to back up paratroopers if they are ordered to evacuate Americans in Zaire.

Sources in Lusaka reported that initial efforts to open negotiations with the rebels for the evacuation of 3,000 to 4,000Europeans living in the war zone had met with no success.

The sources suggested that the Europeans may now be kept as hostages and used as a bargaining chip in the dissident's dealing with Western governments, as well as Zaire authorities.

The other principal Western powers with interest in Zaire - Belgiun and France - were said yesterday to also be laying plans for those parts of Shaba Province affected by the fighting.

However, with Kolwezi's airport in the hands of the rebels, it was not clear how the foreigners would be evacuated.

In late 1964, the United State and Belgium cooperated in an operation to free European hostages being held in Kisangani, then called Stanleyville, by another rebel group. That operation involved U.S. planes dropping Belgian paratroopers on the town and driving the rebel forces from the area.

Both European diplomatic sources in Brussels and spokesmen for the Congo National Liberation Front, the group behind the Shaba insurgency, reported that Kolwezi and railway town of Mutshatsha 60 miles to the west had fallen to the rebels.

But some reports reaching Lusaka yesterday seem to indicate the Zairian army was still holding out in several parts of Kolwezi and that not all Europeans there were captives of the rebels. One report said only a number of males had been rounedd up by the rebels.

The Zairian government claimed that it was still in control of most of Kolwezi and that paratroopers had been dropped into the war zone and other reinforcemens were on the way.

It has called upon France, Belgium, the United States, Morocco and even China to send assistance, but so far there has been no firm reply from any of these countries. Last years, France flew in 1,500 Moroccan troops to Shaba Province during the National Liberation Front'a first unsuccessful attempt to take it over and topple president Mobutu Sese Seko.

Zaire says the Front is armed and supported by Cuba and the Soviet Union and that its forces - 3,000 to 4,000 strong - invaded from neighboring Angola. Zaire and Angola have been bitter enemies ever since the 1975-1976 Angolan civil war when Mobutu backed pro-western factions that lost out to the now-rulling Cuban and Soviet-supported Popular Movement for the Liberation of Angola.

Most accounts of the present fighting seem to back up the Zairian cointention that the rebels came from Angola and probably crossed their attack on Kolwezi. However, Zambia has denied it gave any help to the rebels, or that they passed through its territory.

The struggle for control of Kolwezi is thought to be crucial because of the economic importance of the mining center and the psychological impact its loss would have on the Mobutu government. The National Liberation Front has already stated that its main objective, this years last, is the overthrow of Mobutu.

Once Kolwezi falls, the rebels are expected to move on Tenke, 45 air miles to the east and a strategic road and rail junction for the export of one-third to one-half of all of Zaire's copper. With Tenke in their hands, the rebels would presumably halt all copper exports to the north in the hope of provoking an economic crisis for the Mobutu government.

The rest of Zaire's 450,000 tons of copper is exported through Zambia, Rhodesia and South Africa.

Control of Tenke would also allow the Front's forces to isolate the Shaba Province capital of Lubumbashi and to strike northward toward Kamina, a major Zairian Air Foirces base for its French Mirage jets.

The government was reported to be flying in troop reinforcements to Lubumbashi and to have imposed a curfew on the provincial capital.

Rebel forces are also said to be gathering for attacks on other main towns along the road and rail route west of Mutshatsha leading toward the Angolan border, including Kasaji and Dilolo.

There was no firm evidence yesterday, after six days of fighting, that the Zairian army was having much success in dislodging the rebels from either Kilwezi or Mutshatsha despite the use of its Mirage jet fighters to bomb and strage their positions. The rebel's use of urban guerilla warfare tactics was said to be hampering the use of jets.

However, it appeared from most available reports that the Zairian army, led by the north Korean-trained Kamanyola Division, was fighting much harder this years than last against the rebels. In addition, most reports reaching here and European capitals tend to be 24 hours behind in their information, making the latest situation unclear.

If the Zairian Army fails in the next days to make any appreciable progress in regaining control of Kolwezi and Mutshatsha, outside military addistance, such as the Moroccans privided last year, is likely to become crucial to the survival of the Mobutu government