An Israeli Army officer today accused the personal aide to Defense Minister Ariel Sharon of lying when he claimed he received no reports concerning the Palestinian refugee camps in West Beirut on Sept. 17, the second day of the massacre of civilians in the camps.

Lt. Col. Moshe Hevroni told the judicial board of inquiry into Israel's role in the massacre that Sharon's aide, Avi Dudai, was told of an unconfirmed report of civilian deaths in the camps on that morning by Sharon's acting military aide, Lt. Col. Reuven Gai.

Gai, who also testified before the inquiry board today, confirmed Hevroni's assertion but said that when he spoke to Dudai he had emphasized that the report was unconfirmed. "I said, 'Don't do anything with it,' " Gai told the three-member panel. " 'Since it's not an official report that comes to us, don't put it in.' The reports we transmit are absolutely official."

Hevroni's accusation appeared to implicate Dudai in early knowledge that something was wrong in the Sabra and Shatila refugee camps in West Beirut and suggested that Sharon, too, must have been informed around the same time. But Gai's characterization of how the information was relayed to the Sharon aide suggested that it may have gone no further.

In earlier testimony, Sharon told the inquiry board he first learned of widespread civilian casualties in the camps around 9 p.m. Sept. 17 in a telephone call from Israel's Army chief of staff, Lt. Gen. Rafael Eitan. Sharon said Eitan told him that the operations of the Lebanese Christian Phalangist militiamen inside the camps had been halted by then.

One of the key questions the commission is investigating is when Israeli officials first had knowledge of the massacre and whether they should have acted sooner to remove the Phalangists.

After the massacre, Hirsh Goodman, the military correspondent of the Jerusalem Post, reported that on Sept. 16, the night the militia units entered the camps, a Phalangist commander inside Shatila informed Israeli Army headquarters in Beirut that "until now 300 civilians and terrorists have been killed." Goodman said the report was immediately transmitted to the Israeli Army's central headquarters in Tel Aviv.

It was clear that this was the same report referred to today by Hevroni, the bureau chief for the director of Army intelligence in Tel Aviv. He said he first received it on the morning of the 17th and instructed an aide to relay the information to Gai.

Later the same day, Hevroni said he was with Dudai, who asked him if there was any more information on the report.

"If so," asked the panel chairman, Judge Yitzhak Kahan, "when Dudai testified before us that he did not know of these reports on the 17th until the evening, this was incorrect?" "He is not speaking the truth," Hevroni replied.

Gai testified that the report was first conveyed to him as "gossip" and that "I didn't see fit to do anything with it since I didn't know what the report's credibility was." He did tell Dudai about it, Gai said, and he asked the Army's operations branch whether they had any information on "what's happening in Beirut."

"They said, 'Nothing, we have no reports and that's it,' " Gai said.

Dudai appeared before the board in closed session but a portion of his testimony, in which he said he had received no reports of civilian deaths on Sept. 17, was made public last week. He was with Sharon much of that day, but it remained unclear whether he mentioned the information provided to him by Gai to the defense minister.