The State Department is investigating reports that Argentina authorities may be murdering political prisoners to prevent their testimony before a human rights commission.

The Washington-based Council on Hemisphere Affairs also reported Thursday that the Argentinians are moving large groups of prisoners to clandestine locations.

The council charged that the government is trying to eliminate or hide prisoners before an international human rights commission visits the country early next month.

The commission, part of the Organization of American States, plans to visit Argentina to investigate allegations of government violations of human rights.

Asked about the council's charges that Argentine authorities may be murdering prisoners, an OAS source said he had "heard all kinds of stories," but that the commission was still determined to visit the country.

"It's a lot easier to investigate those things when you're down there," he said.

One State Department official said investigations of the reports are proceeding in Argentina, and that he expected confirmation or denial by early next week.

A spokesman for the Argentine embassy said the reports are not true.

"The government is working very hard on preparation of documents to submit to the human rights commissioner," Hernan Massini added.

The State Department has confirmed reports of five raids last week resulting in the seizure of documents compiled by the Argentine League for The Rights of Man, the Permanent Assembly for Human Rights and the Commission of Families of Persons Missing for Political Reasons.

"We are surprised at these report, particularly on the eve of the visit of the Inter-American Human Rights Commission," State Department spokesman Thomas Reston said. "We hope that the Argentine government will take further actions which might interfere with the commission's visit.

The six-member commission plans to visit Argentinea Sept. 6-20 to investigate allegations of human rights violations in that country. A committee of American lawyers who visited Argentina this year claimed "At least 10,000" Argentina citizens have disappeared since President Jorge Rafael Videla's government came to power in 1976. Amnesty International has estimated the number of disappearances to range from 5,000 to 20,000.

Council on Hemispheric Affairs director Larry Birns called on the AS to abandon its travel plans yesterday, unless the Argentine government promises to stop harassing human rights groups.

"These organizations would have provided the most help to the commission. If they are intimidated, It's going to be very difficult for them to cooperate with the OAS," Birns said.

A spokesman for the Argentine embassy said this week that the State Department failed to make clear in its statement that the police raids were ordered by an Argentinian judge and not directly by the government.

The judge ordered confiscation of the human rights organizations' files in connection with the trial for perjury of a woman allegedly encouraged by officials of the Argentine Human Rights League to give wrong information to authorities about the disappareance of her daughter, the embassy said.