Guatemala's Congress dismissed an opposition petition to annul last week's presidential election because of charges of widespread fraud and voted tonight to declare the government's official candidate, Gen. Angel Anibal Guevara, Guatemala's next president.

With supporters of the former defense minister shouting "Viva Guevara" from balconies of the chamber, Congress President Jorge Bonilla Lopez declared Guevara the "properly elected" victor in last Sunday's national elections on the basis of an almost 103,575 vote plurality in the four-man contest.

Under the Guatemalan constitution, the Congress must pick the next president from among the two leading candidates in the election when--as occurred last week--none of the candidates has a clear majority.

Tonight's vote came after a week of bitter protests from the three losing candidates, who charged widespread fraud in favor of the government candidate. The government has denied the charges and refused all opposition demands for permits to stage street demonstrations against the elections.

In a show of bitterness over the elections, the second-place candidate, Mario Sandoval Alarcon, a former vice president, sought to withdraw his name from the congressional balloting so as not to give the election any legitimacy.

The congressional majority, heavily weighted in favor of the governing coalition, refused Sandoval's demands to withdraw, saying the constitution does provide for such an action. Deputies from Sandoval's party then cast blank ballots when the vote was taken.

With nine other deputies of the 61-member chamber absent, Guevara was chosen by a vote of 39 to 13.

Earlier, the Congress voted, with the same majority, to certify last Sunday's vote tally.

According to the official results approved tonight, Guevara got 35 percent of the popular vote against 25 percent for Sandoval, an extreme rightist. Third in the election tally was former minister Alejandro Maldonado, who received 20 percent of the vote. A fourth candidate, architect Gustavo Anzueto, had 9 percent.

The rest of the one million votes cast were blanks--reflecting a protest by leftists who had denounced the election as nothing but a contest between four conservatives representing only the nation's traditional power structure.

The three losing candidates, in a rare but brief accord, banded together early last week to organize a protest campaign to annul the elections. The three were briefly detained by riot police Tuesday after being tear-gassed when they and their supporters sought to march on the presidential palace to petition outgoing President Romeo Lucas Garcia to annul the election.

The government, stung by the criticisms that have been leveled against the vote, insisted that whatever irregularities there may have been were only "natural" ones that in no way affected the outcome of the election, which they insisted had been open and democratic.

The opposition tonight sought to convince Congress to annul the elections on the grounds of what it said was "fraud, coercion, violence and threats" by voting officials and national police officers at the polls. The opposition has alleged that gross irregularities and outright vote stealing occurred between the time the balloting ended and the locally tabulated results were telegraphed to the capital.

The congressional majority dismissed the opposition petition.

Guevara, and his vice presidential running mate, Ramiro Ponce Monroy, a former mayor of Guatemala City, will take office July 1.

They come to office at one of the most difficult times in Guatemala's recent history. Under Lucas, who like Guevara is a former minister of defense and the choice of the armed forces that dominate Guatemalan politics, Guatemala has come under increasing international pressure because of its record of human rights violations.

In a four-year streak of mounting violence, involving a leftist insurgency in the countryside and extreme rightist death squads often reportedly working for or tolerated by the government security forces, the death toll of civilians in Guatemala has risen to more than 500 a month.