Two Americans making a documentary film on the fighting in Afghanistan reportedly have been killed in an attack by Soviet or Afghan government forces, rebel spokesmen in Pakistan said yesterday.

Conflicting accounts of the incident, which took place Oct. 11 northwest of Kabul, the Afghan capital, were given to U.S. officials in Pakistan on Monday, and State Department spokesmen said they had no confirmation of the reports.

A spokesman for Hezb-i-Islami, the Afghan rebel group with which film maker Lee Shapiro, 38, of North Bergen, N.J., and his sound man, Jim Lindelof, 30, of Los Angeles, were traveling, said the group learned of the incident from Shapiro's wounded interpreter in a rare radio report from a rebel base near Kabul. The spokesman in the Pakistani border town of Peshawar said U.S. officials were not informed until this week because the rebels were awaiting details.

"At first we heard that they had been killed in a Soviet bombardment," a U.S. diplomat in Peshawar said, "but now they say it was an ambush."

More conflicting information was reported by Reuter, which quoted a U.S. official in Washington saying he had a report from an unnamed source that two western journalists had been captured by Afghan government forces and taken to Kabul.

Shapiro and Lindelof had been filming in Afghanistan since May, traveling close to the Soviet border with rebels of the Hezb-i-Islami, one of the most militantly fundamentalist Islamic guerrilla groups. The principal sponsor of their film project was CAUSA International, founded in 1980 by the Rev. Sun Myung Moon to promote anticommunist activities in Latin America.

Antonio Betancourt, a CAUSA vice president, said at a New York news conference yesterday that the organization had put up half of the film's $500,000 budget. Shapiro, a member of Moon's Unification Church, had received CAUSA funding for a documentary on Nicaragua's Miskito Indians that was shown on public television last year.

Lloyd Eby, a trustee of Shapiro's Afghanistan Documentary Movie Project Co., said at the news conference that funding for the film was also provided by the John Olin Foundation of New York and the Lynde and Harry Bradley Foundation of Milwaukee. Officials of both foundations confirmed that some funding had been approved but said they had not known that Moon's organization was the film's principal sponsor.

Eby said Shapiro and Lindelof first went into Afghanistan a year ago, but came out in May to replace their equipment -- lost, by one account, in an ambush they had escaped. They returned to Peshawar at the end of May and crossed the border again.

For Lindelof, this was his third trip into Afghanistan. He had first gone in 1985 to aid wounded mujaheddin as a paramedic.

If the reported deaths of Shapiro and Lindelof are confirmed, they would be the second and third U.S. journalists killed inside Afghanistan since Soviet troops, now estimated at about 115,000, entered the mountainous country at the end of 1979 to help the communist government against the Islamic rebels. The first American killed was Charles Thornton, a medical reporter for The Arizona Republic, shot in an ambush in 1985. Four other journalists have been killed in action in Afghanistan.

A French photographer traveling in northwestern Afghanistan with another rebel group reportedly was captured by government troops this month. The photographer, Alain Guyot, 46, was working for the French photo agency Sygma.

CAUSA's Betancourt said that Shapiro "was told many times that he could be killed, but he didn't care."

"Lee Shapiro was not a man of strong political views," Betancourt said. "The political struggle was secondary to him. The most important thing to him was that people are suffering."

Eby said that Shapiro and Lindelof were almost through filming and expected to return to the United States next month.

James Piereson, executive director of the Olin foundation, a public affairs funding group headed by former treasury secretary William E. Simon, said it had promised to give Shapiro's company up to $50,000 for editing the Afghanistan footage. Piereson said the grant was made because Shapiro's film on the Miskitos was "excellent."

Hillel Fradkin, senior program officer for the Bradley foundation, a 35-year-old Milwaukee community fund that has recently begun supporting national research and educational projects, said its board had approved a small grant for Shapiro's film after seeing some photos and being told that some footage had already been shot inside Afghanistan.

Both Piereson and Fradkin said they had not known that Moon's CAUSA International was the film's principal sponsor. Special correspondents Elaine Parnell in Peshawar and Marianne Yen in New York contributed to this report.