A representative of the Dutch government arrived in El Salvador today to open an investigation into reports that four Dutch journalists killed here Wednesday may have been murdered "in cold blood," rather than in a skirmish between troops and guerrillas as the Salvadoran government had reported.

The government stood by its version of the deaths, while two other tense incidents involving troops and journalists were reported.

At a news conference in The Hague, Dutch Foreign Minister Max van der Stoel, responding to a question about whether the killings were a case of "cold-blooded murder," said: "There are reports to indicate it was."

He added: "When people are shot in cold blood it is a very, very serious matter."

Dutch Ambassador to Mexico Jan Kees Speyart van Woerden, who is also accredited to El Salvador, flew here from Mexico. On arrival this afternoon, he declined to comment on the case. "I have to be evasive, what else would you expect?" he said.

Officials were jumpy about the incident, which the government used as an opportunity to warn foreign journalists here against "imprudently exposing themselves" in areas where the guerrillas operate. The nervousness was demonstrated in two incidents between journalists and security forces.

In one, a Brazilian television team, traveling near the town of San Benito, 39 miles southeast of here, said their vehicle had been fired on by helmeted soldiers running down the road behind them, even though it was flying a white flag and marked as a journalists' car.

In a second incident, a group of 10 journalists who had gone to Santa Rita in Chalatenango Province to investigate the Dutch journalists' killing were suddenly surrounded by a dozen plainclothes men carrying M16 automatic rifles. The men had driven into Santa Rita, where the journalists sought to interview local residents, in a truck mounted with a U.S.-made M60 machine gun.

The journalists were interrogated at gunpoint for 20 minutes about what they were doing in Santa Rita before being allowed to leave to return to the capital.

Although the men repeatedly refused to identify themselves or state under what authority they were questioning the journalists, at least one told a journalist that he was a member of ORDEN, a supposedly disbanded rural force that had traditionally operated as a strong-arm force for Salvadoran landowners and which is often identified as being a major contributor to the "death squads" that have been held responsible for a large number of the more than 13,000 deaths of civilians estimated to have occurred last year.

The bodies of the four dead journalists--Jacobus Andries (Koos) Koster, Hans Ter Laan, Jan Quiper and Johannes (Joop) Willemsen--were embalmed at a private funeral home today, apparently on government orders, to prepare the bodies to be flown back to the Netherlands.

In Amsterdam, Reuter reported, a crowd attacked the U.S. Consulate after a demonstration protesting the killings. A police spokesman said about 100 youths broke away from the 1,500-strong demonstration and threw stones at the consulate. They were dispersed by riot police using tear gas. Most of the consulate's windows were broken, the spokesman said.

Suspicions that the four might have been shot after being captured by the Army, rather than in a clash as officially stated, hinge on the fact that three of the journalists were shot in the face--apparently repeatedly--and the fourth died from a shot in the throat and chest. Such precise injuries, medical sources here said, are too neat to have resulted from a random firefight between the Army and the guerrillas with whom the four journalists are known to have made contact minutes before being killed.

The discovery of several dozen empty M16 rifle shells at the apparent site where the journalists died and where colleagues yesterday found bloodied shirts and jeans, with bullet holes, apparently ripped off the bodies before they were trucked to the Salvadoran capital, also seemed to indicate that the four could have been shot at close quarters.

A Dutch colleague of the dead men who viewed the bodies when they were brought into the central morgue yesterday evening, said it appeared that his friends had been riddled with gunfire at close range--which would not jibe with the official Army report that they were killed during a firefight.

The Salvadoran government, embarrassed by the incident only 10 days before the national election, waited more than 24 hours before publicly confirming the deaths and issuing its explanation.

The Salvadoran government position, stated in a communique issued by the armed forces last night, was that an Army patrol operating near Santa Rita had stumbled upon a group of guerrillas who opened fire on them. In the ensuing 40-minute firefight, the government said, eight people were killed, including the four Dutchmen and a fifth person the government said it suspected was either another, still unidentified, foreign journalist or a "mercenary" operating with the guerrillas.

Friends of the dead Dutchmen who viewed the fifth body at the morgue said it was not that of a foreigner but a Salvadoran who had acted as the Dutch television crew's contact to lead them to a rendezvous with the guerrillas.

According to these friends, the Dutch journalists, the unidentified Salvadoran and a 12-year-old boy were driven from their hotel here Wednesday afternoon to a rendezvous with four armed people who apparently were guerrillas, near Santa Rita, 30 miles north of here. They were driven there by a German colleague who let them off after their contact with the four people at around 5 p.m..

The German, who did not want his name published, said that as the group left the outskirts of the capital, they were followed by a brown Cherokee utility van of the sort often used by plainclothes security forces. The appearance of the van tended to reinforce suspicions that the Dutch television crew was under government surveillance and that their rendezvous with the guerrillas was known in advance by the armed forces.

A brown Cherokee, with tinted windows, identical to the one that followed the Dutch journalists north to Chalatenango, was spotted by other foreign journalists yesterday parked by an Army detachment near Santa Rita.

The Dutch journalists were believed to be under surveillance because they had been interrogated March 11 by Col. Francisco Moran, head of the Salvadoran Treasury Police, about their alleged contacts with guerrillas. The interrogation had been prompted by the discovery of a note listing Koster's name, hotel and room number, apparently found in the pocket of a guerrilla killed in another province two weeks ago.

According to a document that both Koster and Col. Moran signed after the interrogation, Koster had denied knowing any guerrillas, and the four journalists testified that they had not been mistreated or threatened during their interrogation.

The Treasury Police, one of four armed security forces in El Salvador, have repeatedly been accused by Salvadoran and foreign observers of killing civilians whom they have suspected of being linked to the guerrillas.