Chile-ans appeared to have given President Augusto Pinochet a resounding victory in today's referendum which he called to strengthen his hand against foreign and domestic critics.

Gen. Pinochet called a press conference to declare that the support was more massive than he expected. He promised Cabinet changes and a new direction for the ruling four-man junta of military service chiefs, two of whom opposed his calling the plebiscite.

First official returns announced by the Interior Ministry after polls closed at 4 p.m. reported 439.744 "yes" votes against 101,989 "no" - or 81 per cent of the early ballots cast to "support President Pinochet in his defense of the early ballots cast to "support President Pinochet in his defense of the dignity of Chile." Opponents of the military junta have charged that the wording of the question makes a "no" vote appear upatriotic.

Efforts to project totals in the hastifly improvished voting indicated, however, that a large percentage of the voters abstained.

After Pinochet called for the plebiscite on Dec. 21 - in response to a U.N. resolution that, with U.S. support, condemned Chile for human rights violations - the government said voting would be mandatory.

At the last minute, however, after political parties called for a "no" vote, the government dropped plan to enforce reprisals against nonvoters.

Government estimates of the number of voters eligible have varied from 4.5 million - the number that voted in the last free election almost five years ago - to 6 million. Voting lists were destroyed after the military coup of 1973 and the citizens were permitted to vote by presenting their national identification cards.

Independent observers checking at random among the more than 20,000 polling places reported that the tabulation appeared to be fair. However, there was no such verificiation of procedures as the totals were passed up to the Interior Ministry.

Long lines formed at Santiago polling places, including the national stadium where supporters of President Salvador Allende were imprisoned by the thousands after 73 coup. Allende died in military takeover.

Army troops kept the lines orderly, but a fracas broke out at the elementary school where Pinochet voted when supporters shouting "Viva Pinochet" nearly overturned ballot boxes in their effort to press near him.

The Roman Catholic Church, in addition to outlawed political parties, criticized the referendum, known officially as the "national consultation"

If there was any doubt as to how Chileans were expected to vote, it was dispelled by the text of the referendum question, which read:

"In the face of the international aggression unleashed against the government of the homeland, I support President Pinochet in his defense of the dignity of Chile, and I reaffirm the legitimacy of the republic to conduct in a sovereign way the process of the institutionalization of the country."

The vote was meant to be simple affirmation of support and imposed no obligations on Pinochet to residn or reform should he fail to win the backing he sought when he called the referendum two weeks ago.

Still, both the government and the opposition saw it as putting Pinochet's prestige on the line.

Former Allende supporters and CHristian Democratic former President Eduardo Frei criticized the referendum as unfair and urged voters to either boycott it or vote no.

Clashes between Pinochet supporters and opponents erupted in Santiago last week and continued through yesterday.

A bomb damaged the Santiago offices of IBM early today but caused bo casualties.

The referendum provoked a strain within Pinochet's junta when air force Gen. Gustavo Leigh and navy Adm. Jose T. Merino, indicated that the attempt to demonstrate Pinochet's "popular support" would further harm rather than enahance Chile's image abroad.

Leigh and Merino tried to prevent Pinochet from convoking the plebiscite, according to letters attributed to them that circulated last week. Among other things, Leigh said it would d amage the prestige of the military and Merino said it could reopen the country to political activity. Both accused Pinochet of exceeding his powers by calling the vote without full junta support.

Some opponents thought Pinochet would try to use a large favorable vote as an excuse to assume greater power and reduce the influence of other junta members. He insisted, however, that he sought no personal gain in the vote and merely w anted it for the national good.

Despite the restrictions, the referendum brought an atmosphere here that had not seen since the military takeover.

Walls were covered with posters calling on the people to vote for the government, while thousands of leaflet were distributed in the streets telling them to cast negative votes.

A survey among people waiting in line to vote showed that most were happy about casting ballots again, but uncertain about how their votes might be interpreted.