Allegations by refugees from East Timor that Indonesian troops may have killed as many as 100,000 persons - or over 15 per cent of the former Portugese colony's population - will be investigated by a U.S. House committee.

Rep. Donald M. Fraser (D-Minn.) announced yesterday that his subcommittee on International Organizations will hold a hearing March 23 about the accusation that the Indonesians carried on indiscriminate slaughter and committed other atrocities following their December 1975 occupation of East Timor.

The heating is to determine whether U.S. military equipment may have been used illegally in the takeover. Congress has imposed restrictions on the use of American military equipment sold or given foreign countries.

Among the hearing witnesses will be James Dunn, a former Australian consul in East Timor who has done extensive reporting about the situation there.

Dunn's accounts of what the refugees told him about the Indonesian occupation give a picture of an army out of control, engaging in Wanton slaughter, rape and looting. Boatloads of stolen goods were sent back to Indonesia, the refugees said.

Dunn is head of the foreign affairs branch of the Australian Parliament's legislative research service. Some of his work on East Timor, however, was done on behalf of nongovernmental charitable agencies in Australia.

The reports of atrocities have stirred up a political furor in Australia. A bipartisan group of nearly 100 members of Parliament have written President Carter asking that he use his influence with Indonesia to stop the alleged killings and violations of human rights.

The House subcommittee probe grew out of a letter sent to Fraser by six members of the Australian House and Senate, including Tom Uren, deputy leader of the oposition Labor Party.

Dunn's most recent study, issued last month, said the refugees' accounts of Indonesian behavior in East Timor suggest that the plight of these people might well constitute, relatively speacking, the most serious case of contravention of human rights facing the world at this time.

"Reports have one-sixth of the population may have been killed are impossible to assess, let alone authenticate, but the fact that such reports persist serves to highlight the magnitude of the tragedy of Timor."

Leaders of a group of Timorese refugees in Portugal said reports that 100,000 people were killed were "credible, because of the killing in the mountains and because of the extensive bombing," Dunn said.

Indonesia has denied any military takeover of East Timor, which shares the island of Timor with an Indonesian province. Jakarta's version of what happened is that "volunteers" from Indonesian military services went to assist a Timorese political group, Apodeti, in a civil war with a "Maxist-controlled" rival faction, Fretilin.

Specific atrocities reported by refugees include the killing of residents of entire villages as Indonesian forces moved into mountain areas where Fretilin guerrillas were operating; execution of a family because the Indonesians had heard they gave a chicken to Fretilin soldiers; and the shooting of residents because, troops reportedly believed, "they were infected with the seeds of Fretilin."

A special intelligence unit of the Indonesia military working out of the top floor of the Tropical Hotel in Dili, the capital, was said to resort regularly to the use of torture to get information.

In the first days of the occupation of Dili, the refugees said, Indonesian paratroopers carried out mass executions on the city's wharf.

From the refugee accounts, Dunn says, it appears that the Chinese community in East Timor was a particular target of Indonesian hostility in the early days of the occupation. The Chinese, who dominated the former colony's commerical life, lived chiefly in the larger towns.

The Indonesians, with 30,000 troops, are said to have physical control of only about 20 per cent of the area, chiefly the larger urban areas. The Fretilin guerrillas, estimated at about 2,500 but believed to have many sympathizers, are thought to operate in much of the countryside and reportedly make frequent hit-and-hit raids.

A provisional government of native Timorese has been established but refugees say real authority rests with the Indonesian military command in Dili.

Indonesia's takeover followed 20 months of internal political turmoil growing out of the coup that ousted the former dictatorship in Portugal.

Jakarta initially indicated support for an independent East Timor, but then the military leadership in Indonesia became concerned about the presence of an economically and politically weak country on its doorstep vulnerable to outside pressures.