Some of the 50 Americans starting their fifth week as hostages of militant Iranians have been moved out of the U.S. Embassy and are being held elsewhere, diplomatic sources said today.

There has been no official Iranian confirmation that the hostages have been dispersed. But Foreign Minister Sadegh Ghotbzadeh, Revolutionary Guard commander Abu Shaif and the radical Islamic students occupying the embassy, all hinted as much.

Several diplomatic sources suggested that as many as 22 of the 50 hostages taken when the embassy was seized on Nov. 4 have been moved away from the compound. There was no indication who these hostages were.

The diplomatic sources said one group had been seen at Revolutionary Guard barracks in northeastern Tehran and others were being held in private homes.

Rumors have circulated here for days that eight cells were being prepared at Evin Prison, where SAVAK, the now-disbanded secret police, tortured prisoners during the reign of Shah Mohammad Reza Pahlavi, whose return for trial the militant students are demanding.

The reports came as Iran began two days of voting on a controversial new constitution that would make Iran an Islamic theocracy, conferring virtually full governing powers on the Moslem clergy in general and giving Ayatollah Ruhollah Khomeini supreme authority for life.

Although approval of the constitution is expected, strong opposition became evident today in demonstrations in areas of the country where the large minority populations live. In Baluchistan, an official told reporters by telephone that "if we get 4 to 5 percent turnout, we shall be lucky."

In the holy city of Qom, eyewitnesses said Khomeini, looking pale and possibly ill, appeared taken aback when a group of supporters of Ayatollah Kazem Shariatmadari, and Azerbaijani leader and rival of Khomeini, waved dozens of portraits of Shariatmadari in front of Khomeini's car as he headed for the voting booth.

The first indication that all the hostages were no longer at the American embassy surfaced Nov. 25 when Rep. George V. Hansen (R-Idaho) visited the 27-acre compound and said he saw fewer than 20 hostages.

Two weeks earlier, a four-man diplomatic team had seen almost all the hostages at the embassy.

Left unclear was whether the radical students retained their control of those hostages said no longer to be in the embassy.

If some hostages actually are under more orthodox control, optimistic analysts suggested this might be an opening for loosening the students' grasp on the situation.

If the hostages in Revolutionary Guard custody were put on trial, some analysts argued, they could be expelled even if found guilty of espionage charges.

However, members of the diplomatic community were fearful that knowledge of the dispersal of the hostages might trigger some impulsive U.S. reaction.

Asked about the health of the hostages, diplomatic sources said they had no definite information, "but what we know is not at all encouraging."

In reply to President Carter's charges of ill-treatment of the hostages, Ghotbzadeh said: "They are all safe and sound. As for their geographic location, it's none of your business."

A spokesman for the students holding the embassy said: "I don't know where they are. Maybe they are at the embassy, maybe not."

The Revolutionary Guards' military commander said enigmatically, "I am responsible for the security of all the people in Iran -- even the hostages -- wherever they are.""

Meanwhile, the first day of voting in the controversial constitutional referendum was marked by seemingly modest turnouts in Tehran and reports of wholesale protest demonstrations, boycotts and violence in the provinces.

Potentially the most disturbing opposition was a march by tens of thousands of Iranians in Tabriz, capital of the northwestern province of Azerbaijan where a third of the country's population lives. Azerbaijan borders on the Soviet Union.

Shariatmadari has called for a boycott of the referendum, and if his avice is heeded, Khomeini's hopes for an overwhelming "yes" vote would be doomed.

Together with Azerbaijan, other national minorities in Kurdistan, Khuzestan, Baluchistan and the Turkoman country are expected to boycott the referendum. Their populations amount to roughly half of Iran's total.

Among other groups boycotting the election were westernized women protesting against second-class status, the Jewish association, which termed the constitution dictatorial, as well as political groups ranging from right and centrist parties to the armed leftist guerrilla organizations, such as the Marxist Fedayan and the Islamic Mudjahideen.

Within the leftist spectrum, only the Tudeh, or pro-Moscow Communist Party, has called for a "yes" vote.