Angry charges of fraud today exacerbated the already mounting tension in Nigeria over the slow, partial release of voting results from Saturday's inconclusive, six-way presidential election.

While the returns released so far are inconclusive, it is clear that the front-runners are two of the six candidates, incumbent Shehu Shagari, 58, and Obafemi Awolowo, 74, whom Shagari narrowly defeated in 1979.

With results in from 11 states, Awolowo was leading with 7.11 million votes to Shagari's 6.09 million, but figures have not been released yet from northern states in which Shagari is heavily favored.

Nigeria's election has been considered an important test of stability for one of Africa's most influential nations, which is an important oil producer and the second-leading exporter of petroleum to the United States. If Awolowo should win, however, no major changes in foreign policy are expected, as the election is being contested largely on domestic economic issues.

Two other candidates, neither of whom was expected to win, have charged that their supporters were not allowed to vote because of numerous administrative foul-ups by the Federal Electoral Commission during the voting. The commission is also a growing source of ire among Nigerians because by early this morning--more than 24 hours late--results from only 11 of 19 states plus the unimportant federal territory had been released.

The two complaining candidates, Nnamdi Azikiwe, 78, Nigeria's first president after independence was granted by Britain in 1960, and Waziri Ibrahim, 57, alleged that the widespread voting hitches were intentional and rigged the results against their candidacies.

Azikiwe, from Ibo-dominated Anambra State, threatened in an interview yesterday with the News Agency of Nigeria to invoke available constitutional means "to show the world the people of Anambra were not given the chance to vote massively."

Anambra is part of the one-time breakaway state of Biafra.

Yesterday, the high court of Anambra State granted Azikiwe an injunction against the Federal Electoral Commission by ordering it not to release results from that state. Azikiwe charged that of the 3.3 million registered voters in Anambra, fewer than 1 million were able to vote because of the electoral commission's poor administration of the election.

In a survey of three cities--Lagos, Enugu and Kaduna--during Saturday's balloting, reporters found that many Nigerians were unable to vote on time or not at all because of missing or inaccurate registration lists or the late arrival to the polls of election officials and police-escorted ballot boxes.

Ibrahim said in a press conference outside the electoral commission's headquarters today that he will seek a court injunction during a hearing scheduled for Wednesday that will overturn the entire results of and call for a new election.

Saturday's election involved millions of voters. Nigeria's estimated population total of 100 million makes this Africa's most populous nation. It was the second such election since the Army returned the country to civilian rule four years ago. The elections this year are the first ones run by civilians since 1966, and the fraud charges raise the specter of a repeat of violence that year that led to the overthrow of civilian rule.

The election commission claimed to have registered 65 million voters, a figure that many observers said appeared greatly inflated by padding and counting errors. There were 48 million registered voters in 1979, and even that figure was considered high.

Saturday's presidential election was the first of five polls involving about 12,000 candidates slated for successive weeks here in one of the rare multiparty democracies on the continent. In the coming weeks, Nigerians will elect state governors, representatives to each of the two houses of the National Assembly and state assembly deputies.

Figures released in the first six states counted indicated that 58 percent more Nigerians voted this year than in 1979. So far, votes have been counted in the projected federal capital, Abuja, and in 11 states--Lagos, Niger, Bauchi, Ondo, Ogun, Kwara, Imo, Oyo, Rivers, Cross River and Bendel.

Nigeria's first civilian government was overthrown by the Army six years after independence after widespread vote-rigging led to rioting in the southwestern Yoruba region.

In subsequent years Nigeria experienced two more coups, a tragic civil war that cost about 1 million lives and another coup attempt before the Army restored civilian rule after 13 years. Before the handover, however, the Army supervised the 1979 elections leading to civilian government. A new constitution, modeled, in part, after the U.S. Constitution, was put into force.

Although Azikiwe ran a distant third in the 1979 presidential contest, and so far is running about the same in this year's election, the votes of his Ibo homeland have not been released yet. But this year's presidential election is also a key test of the candidates' abilities to appeal to voters across the country's traditional ethnic lines, as the winner must gain a plurality of the national vote and win at least 25 percent of the vote in two-thirds of Nigeria's 19 states.