An obviously overjoyed Yasser Arafat wound up two days of meetings with leaders of Iran's revolution here today and said the overthrow of the shah by a militantly Moslem movement offered a "new dawn and a new era" to the Middle East struggle.

Just hours after Arafat met with the new Cabinet, Iran broke diplomatic relations with Israel, according to the Iranian news agency. Iran ordered all Israeli diplomats and citizens to leave the country and it recalled Iranian diplomats from Tel Aviv.

Radio Iran quoted Prime Minister Mehdi Bazargan as saying that the break was "fully in keeping with the policy announced before we came to power of cutting all ties with Israel."

In a triumphant gesture today, Arafat visited the building that housed the Israeli mission in Tehran and claimed it as the local office of the Palestine Liberation Organization, the umbrella Palestinian group that he heads.

He told reporters that the change of government in Iran had radically altered the Middle East power balance and had turned "the whole policy and strategy in the region upside down."

While the long-term implications of Iran's move to a position of firm support of Arafat are not immediately clear, the change does represent a setback for Israel, which enjoyed the exiled shah's tacit support in many areas, including the supply of petroleum.

Arafat's whirlwind visit to Tehran came amid these other developments:

In the second day of a massive evacuation, 802 more Americans were flown out of Iran to Europe.

Radio Iran, in an announcement that perplexed observers, said former premier Shahpour Bakhtiar was the target of a manhunt. Earlier government reports had said Bakhtiar was in custody.

Even more telling than Arafat's buoyant mood in his press conference was a photograph printed in Iranian newspapers. It showed him in an embrace with a beaming Ayatollah Ruhollah Khomeini, the normally dour longtime ally and now leader of Iran's militantly pro-Palestinian revolution.

Arafat brushed aside suggestions that conservative Arab monarchies such as Saudi Arabia, Kuwait or the United Arab Emirates -- oil-rich states that help finance his PLO -- were threatened by Iran's revolution.

In the past, members of Khomeini's entourage have expressed their desire to undermine their conservative Arab neighbors across the Persian Gulf.

But the overthrow of Shah Mohammad Reza Pahlavi obviously heartened Arafat since the monarch for more than a generation had backed Israel against the Arabs in general and the Palestinians in particular.

Israel is now not only deprived of the longtime source of 60 percent of its oil imports, but also faces the added threat of militant Iranian support for the PLO.

Insisting that Iran "is my second home" -- after Palestine itself -- Arafat, dressed in field jacket and black-and-white keffiyeh, or headdress, hailed the common goals of Iranians and Palestinians.

They representated "two revolutions in one revolution and two peoples in one people," he said. It was a phrase he repeated when asked if he expected the now badly disclocated Iranian armed forces to help the PLO in any future conflict with Israel.

"I leave it to American computers to analyze what I said," he remarked amid laughter.

"The Voice of the Islamic Revolution," as Radio Iran now calls itself, answered the question more forthrightly, using Khomeini's favorite theme of the need for militant Islamic solidarity.

"The Iranian revolution can be safeguarded only if we remember to send assistance to freedom fighters all over the world," a radio commentary said. "Certainly, in sending men to fight side-by-side with the fighters on Islamic fronts, the PLO will hold a special position."

For more than 20 years Khomeini has already defended the Palestinians against Israel, in part, observers are convinced, because of the aid the Jewish state provided in establishing SAVAK, the once-dreaded secret police, which drove the ayatollah into exile in 1964.

Describing the Iranian revolution as an "earthquake" felt round the world and as a "glorious torch that will enlighten the whole region," Arafat said, "You have done something that seemed impossible and that has frightened the United States and Israel."

"Today, Iran, tomorrow Palestine," was a theme he developed throughout the first 24 hours of a visit that began last night when he arrived unannounced from Beirut and Damascus and conferred with Khomeini.

Today, he met with Bazargan's Cabinet, visited the former Israeli mission, which now will house the PLO office, and made a pilgrimage to Behest Zehra cemetery, which has become the shrine of the Iranian revolution.

Mobbed in late morning when he arrived nearly four hours behind schedule and again upon his departure from the cemetery, 20 miles south of Tehran, Arafat told a crowd of some 2,000 Iranians that "the road to Palestine now leads through Iran."

At one point the milling crowd was packed so close to Arafat's Mercedes that only entreaties by Khomeini's son, Ahmed, succeeded in restoring order, allowing Arafat to emerge and speak through a bullhorn from atop an ambulance.

At his news conference, Arafat constantly praised his Iranian allies, the right-wing Moslem guerrilla movement known as the Mudjahideen, and refused to be drawn into suggested mediation between them and their sometime Marxist allies called the Fedayeen.

He insisted that differences between the two extremist groups -- and between them and Khomeini -- were exaggerated. He declined to spell out the aid the PLO had provided his Iranian proteges.

There have been suggestions that Arafat's mainstream Fatah organization trained and perhaps helped arm the Mudjahideen while George Habbash's Marxist Popular Front for the Liberation of Palestine provided similar aid to the Fedayeen.

Meanwhile, the airlift's second day went more smoothly than the first as more than 800 Americans and 240 Britons were flown out on government-sponsored flights. Hundreds more foreigners left on regularly scheduled commercial aircraft.

However, American officials said Iranian revolutionary authorities indicated they could not guarantee the timing of special evacuation flights after tomorrow although the princile of the airlift itself was not under question.

Flight congestion problems were blamed, as Mehrabad Airport is only slowly returning to normal after a seven-week strike by civilian air controllers.

Sworn in to the Cabinet today and presented to Khomeini by the prime minister were Yadollahi Sohabi, minister for revolutionary planning; Agriculture Minister Mohammed Izadi, Commerce Minister Reza Sadr and Power Minister Abbas Taj.

They were relative political unknowns except for Sohabi, who is credited with planning many of the strikes that undermined the shah's rule in its final months.

More arrests of ranking officers of the armed forces were reported in the provinces.

In Tehran more than a thousand Fedayeen marched to Khomeini's headquarters to back demands for full purges of the m ilitary establishment and creation of a "peoples army."

Such militant pressures succeeded in forcing Bazargan's government into replacing only recently named Navy, Air Force, police and gennarmerie commanders with men more acceptable to the radical left.

The extremists have played on junior officers' and other ranks' resentments against the new government for naming senior officers once loyal to the shah to important commands.

Meanwhile, the government announced that former prime minister Bakhtiar, swept aside in last weekend's insurrection, was not under arrest and was still being sought.

Earlier, revolutionary authorities had insisted that Bakhtiar was in custody. No explanation for the seeming inconsistency was provided.

There was no immediate Israeli reaction to Iran's announcement that it was breaking diplomatic ties. Under the shah Israel maintained a trade office in Tehran that functioned as a diplomatic mission, according to Reuter. The building was ransacked by anti-shah revolutionaries last weekend but it had already been evacuated by the Israelis.

[The Iranian government announcement said the explulsion order was against "Israeli experts and employees of the Israeli national airline, E1 A1," which until recently flew regularly scheduled flights from Tel Aviv to Tehran. It was not clear whether the explulsion order had already been carried out.]