TEHRAN, AUG. 2 -- With more than a million angry Iranians massed in front of parliament, Speaker Hojatoleslam Ali Akbar Hashemi Rafsanjani today intensified Iranian threats against Saudi Arabia, vowing to "uproot Saudi rulers" to avenge the deaths of 275 demonstrating Iranian pilgrims in the holy city of Mecca on Friday.

"We, as soldiers of God and implementers of divine principles, oblige ourselves to avenge these martyrs by uprooting Saudi rulers from the region," Iran's official Islamic Republic News Agency quoted Rafsanjani as saying.

Rafsanjani's statements came after Saudi Arabia said it had turned back a high-ranking Iranian delegation that flew to Mecca today to investigate Friday's clashes between Saudi police and Iranian demonstrators, during which 402 persons were killed and more than 600 injured, according to official Saudi estimates.

The violence and Iran's subsequent threats against Saudi Arabia and the United States have further fueled the already sharp tensions in the gulf and stirred apprehensions about a revival of bloody animosities between Islam's two main sects, the Sunnis, who predominate in Saudi Arabia, and the Shiites, the majority in Iran.

Tehran radio said Iranian Interior Minister Ali Akbar Mohtashemi sent a message to his Saudi counterpart, Prince Nayef ibn Abdulaziz, threatening to avenge the Mecca violence and saying Iran would also retaliate against the United States.

{Iran said that seaborne forces of the Revolutionary Guards this week would conduct "martyrdom" maneuvers in the Persian Gulf and the perilous Strait of Hormuz, toward which two U.S. Navy warships were escorting the reflagged Kuwaiti tanker Gas Prince.

{The tanker, loaded with liquefied gas, was at the halfway point in its 2 1/2-day journey through the gulf to the Strait of Hormuz, said the commander of the U.S. Navy's Middle East task force, Rear Adm. Harold Bernsen.

{An Associated Press pool report from the USS LaSalle off Bahrain quoted Bernsen as saying three more of 11 Kuwaiti tankers to be placed under U.S. naval protection would be reflagged within the next 10 days. He said the danger of mines was considered high in some parts of the gulf, as was the threat of attacks by Iranian patrol boats, possibly on suicide missions.

{In Beirut, the pro-Iranian Islamic Jihad issued a statement threatening the Saudi ruling family with reprisals for the violence against the pilgrims Friday and warned that the United States will suffer the consequences for the policy of its "lackeys" in the area, meaning Saudi Arabia, Washington Post special correspondent Nora Boustany reported. The statement was accompanied by a photograph of American hostage Terry Anderson, whose kidnaping in March 1985 was claimed by Islamic Jihad.

{In Kuwait, the U.S. Embassy, which was bombed by Moslem extremists in 1983, received a bomb threat and was evacuated briefly. Staff members said no bomb was found, Reuter reported.}

The official Saudi Press Agency, reporting from Jeddah, said the Iranian delegation was received yesterday "in the hope that it would apologize" for Iran's role in the Mecca violence and for the storming yesterday of the Saudi Embassy in Tehran by crowds angered by reports of the deaths in Mecca. The French and Kuwaiti embassies also were attacked.

There was no word on the fate of four Saudi diplomats who reportedly were detained in Tehran when a mob ransacked the Saudi Embassy.

The Iranians returned home, the Saudi news agency said, quoting an official source, after it became clear that its purpose was solely "to investigate matters touching on the sovereignty . . . of the kingdom" that Saudi Arabia believed could be discussed through the Iranian Embassy and the chief of Iran's delegation to Mecca.

Tehran radio said that the Iranian delegation had been asked on arrival to meet with Saudi officials, "but the delegation refused this because of the Saudi government's involvement in the massacre and decided to return to Tehran."

Iranians say that Saudi police opened fire on the demonstrators, killing hundreds and injuring thousands of Moslem pilgrims. The Saudi information minister said yesterday that "not a single bullet was fired" and that the victims were trampled when Iranian pilgrims stampeded. Saudi television broadcast 15 minutes of film that it said showed the progress of the Iranian demonstrators until they began pelting Saudi police with rocks near Mecca's Grand Mosque, the holiest site in Islam.

"We have no doubt that this massacre was undertaken at America's behest in response to its repeated humiliations in the gulf," Rafsanjani told the Iranians demonstrating here on an officially designated "day of hatred" against the United States, which Iran said was behind Friday's violence. The State Department yesterday called the Iranian charges "baseless."

The Saudi Cabinet held an emergency meeting yesterday and issued appeals to the world's Moslem leaders to condemn the behavior of the Iranian pilgrims.

Several Arab leaders condemned Iran today for the riots in Mecca, but Libyan leader Moammar Gadhafi publicly supported an Iranian demand to place Moslem holy places in Saudi Arabia under "international administration."

Iran has criticized Saudi administration of Mecca, birthplace of the Moslem prophet Mohammed, since Moslem extremists took control of parts of the Grand Mosque during the pilgrimage in November 1979. The ensuing battle, in which 229 people were killed, lasted for nearly two weeks before Saudi forces retook the mosque.

President Hafez Assad of Syria, Iran's main Arab ally in its war with Iraq, sent a message to King Fahd expressing regret for the riots.

The Saudi Press Agency said King Fahd had received pledges of support over the telephone from the leaders of eight other Arab countries.

In Lebanon, about 5,000 supporters of the Shiite Moslem extremist group Hezbollah marched through the ancient city of Baalbeck, in the Syrian-controlled Bekaa Valley, to protest the Mecca deaths, chanting slogans condemning Saudi Arabia, the United States and France.

The Saudis have warned Iran's 150,000 pilgrims still in Mecca -- with an estimated 2 million pilgrims from other countries -- that no further demonstrations or gatherings of any kind would be tolerated. But Hojatoleslam Mehdi Kharroubi, Khomeini's representative at the pilgrimage, was quoted by Tehran radio as saying that the Iranians would "fight to the last man."