Revolutionary authorities executed seven former officials of the deposed shah early this morning, bringing to 28 the number of people killed by firing squad during the past two days.

This latest round of executions put new pressure on the government of Prime Minister Mehdi Bazargan and raised fears of a fresh wave of death sentences.

It also appeared to undermine recent statements by Bazargan promoting an amnesty for officials of the previous government whose crimes basically were participation in the government under the shah or the political party he created.

Among those executed this morning was Habiballah Elghanian, a well-known businessman accused of having contacts with Israel, according to the Voice of the Islamic Republic radio. Another was a casino owner and the rest were police or Army offcials.

Iranian authorities reported early Monday morning that 21 former officials were executed, the largest group to face the firing squad since the revolutionary government came to power in February.

The 21 included two former information ministers and a speaker of the lower house of parliament who was also the last head of the shah's Rastakhiz Party.

The rest were Army officers, police officials or members of the hated SAVAK secret police accused of involvement in massacres and torture.

All 21 were charged by secret revolutionary tribunals with "corruption on earth" and "waging war on God and his emissaries" - accusations that have become routine in the clergy-controlled courts. But this time the judges added a new charge, "insulting the imam," meaning Ayatollah Ruhollah Khomeini. This appeared to raise the prospect of further broadening the scope for capital punishment beyond the vague Koranic notions already in use.

Shortly after the dawn executions were announced by the state-run radio, Bazargan's spokesman, Deputy Prime Minister Abbas Amir-Entezam, issued a statement canceling his thrice-weekly press conference until further notice. There was no immediate explanation and officials would not say whether it was related to the latest shootings.

Interior Minister Ahmad Sadr Haj Javadi privately expressed displeasure Monday over the executions and indicated he had been informed of the death sentences before they were carried out, a well-placed political source said.

Abdol-Karim Lahiji, the head of the Iranian Human Rights Committee, said he was "surprised and shocked" by the executions, which brought the number of those shot so far to at least 192.

The capital charge of insulting Khomeini served to underscore criticism from some quarters here that the trials are mainly to exercise the ayatollah's personal vengeance.

Bazargan recently called for an end to the "spirit or revenge" in Iran and powerful Revolutionary Council was preparing statutes for a limited amnesty. He said the amnesty would not cover those convicted of ordering or taking part in "massacres of the people, torture of prisoners, treason and theft of national property," but would spare officials held for their links with the past government.

Political observers also saw the latest executions as an attempt by the new Islamic rulers to outmaneuver the increasingly critical Iranian left in the absence of any real progress toward solving the country's severe economic, political and social problems.

What is being perceived as Khomeini's "more-revolutionary-thanthou" approach came as the Iranian Tudeh Communist Party openly criticized the Bazargan government of the first time. The party accused the government of siding with capitalists and deviating from the revolutionary path.

Although they have been condemned by liberals and intellectuals, the executions have won broad popular support among the populace and have been praised by leftist guerrilla factions.

Khomeini today issued what was interpreted by some observers as a veiled warning to the left, saying: "Should I allow it, those stagnant roots which are still active in our country would be exterminated in half a day."

In a separate speech, Bazargan appeared to blame leftists for the May Day assassination of a top Khomeini aide. He said Ayatollah Morteza Motahari had been "a victim of the struggle against Marxism." CAPTION: Picture 1 and 2, A former officer in the Iranian secret police, center of left photo, makes an appeal; right, former Army brigade commander hears charges. Both were executed. Photos by UPI