State Department officials yesterday released a report charging that the Soviet Union has "flagrantly and repeatedly" violated international treaties by waging chemical warfare in three Asian nations. They appealed to the world community to join in trying to force a halt to such warfare.

More than 10,000 people have been killed by Soviet chemical weapons in recent years, according to the 31-page report.

It was delivered simultaneously to Congress and the United Nations to back up six months of public charges by the Reagan administration about the Soviets' use of chemical weapons in Laos, Kampuchea (Cambodia), and Afghanistan.

Past charges and presentations by the State Department have been received skeptically because of the weakness of the evidence, which consisted chiefly of a single leaf and stem sample said to show the effects of chemical weapons. The new report is intended to convince skeptics of the firmness of the evidence.

A six-member State Department mission will deliver the report and several hundred pages of supporting classified documents to European and Asian nations next week in the hope of enlisting international support for its campaign.

The Soviets, responding through the Tass news agency, last night branded the reports as "dirty lies," the Associated Press reported.

The Soviets did not dispute that toxins were used in Afghanistan but said they were supplied by the United States to "bandit units," a reference to anti-Marxist guerrillas fighting Afghan government forces and an estimated 85,000 to 100,000 Soviet troops, AP said.

Three or four other nations already have collected and begun studying samples of the deadly chemicals from Asia, according to Richard Burt, director of the State Department's Bureau of Politico-Military Affairs. Canada has delivered samples of "yellow rain" toxin to the United Nations, Burt said.

Burt said there was "absolutely no connection" between his charges against the Soviets and the new push to rebuild the U.S. stockpile of chemical weapons.

"Our primary desire is to raise this issue of the Soviet chemical attacks higher on the international agenda," he said.

The report presents newly unclassified intelligence information about chemical weapons and how they have been used, and says "high officials" of the Soviet chemical corps have been directing chemical attacks in the three Asian nations.

"The Soviet Union and its allies are flagrantly and repeatedly violating international law and international agreements," Walter J. Stoessel, deputy secretary of state, said at a briefing yesterday.

"If the world fails to halt this activity in Laos, Kampuchea, and Afghanistan, it will have little chance to prevent its repetition in other lands, against other peoples," Stoessel said. "Only an alert and outspoken world community . . . can bring sufficient pressure to bear to halt these violations of law and treaty."

"With the publication of this report, the world community has been alerted. The United States will continue to be outspoken; we are confident that other nations, as they recognize the danger, will do likewise," Stoessel concluded.

"The judgments in this report are unequivocal," Burt told the Senate Armed Services Committee.

"Based upon information dating back to 1975," Burt said, "the U.S. government has concluded that selected Laotian and Vietnamese forces, operating under Soviet supervision, have, since 1975, employed lethal chemical and toxin weapons in Laos; that Vietnamese forces have used lethal chemical and toxin agents in Kampuchea; and that Soviet forces have used a variety of lethal chemical warfare agents, including nerve gases, in Afghanistan since the Soviet invasion of that country in 1979."

In preparing the report, the State Department took reports of chemical warfare attacks and deaths and checked them against independent information such as known troop or aircraft movements and weather reports.

"The good evidence in the report is the human testimony," State Department official Gary Crocker told the committee.

"If refugees reported an attack with a certain kind of aircraft, we checked to see if there was one in the area at that time. If there was a report of spraying, we checked the weather in the area at the time."

He said only such double-checked reports of attacks were included in the report, and while there were probably thousands more killed, the number the State Department could verify was 6,504 in Laos, 3,042 in Afghanistan, and 981 in Kampuchea.

Crocker said he was astonished at how the indepedent evidence corroborated the stories of refugees, journalists, and soldiers about chemical attacks.

The intelligence information presented yesterday included a detailed report of the unloading of chemical munitions at the dock in Ho Chi Minh City in Vietnam. The chief of security for the dock defected to the West and related an incident in which crates of three-foot, nylon-wrapped chemical canisters were broken open by workers who wanted to see if there was anything worth pilfering.

The workers were quickly warned not to go near the canisters because they were "deadly toxic chemicals," the security chief said.

The report also described information that came from autopsies on victims of an attack with "yellow rain"--the poison extracted from fungus and reportedly the chief agent now used in chemical warfare in Southeast Asia.