ISLAMABAD, PAKISTAN, OCT. 25 (THURSDAY) -- Former Prime Minister Benazir Bhutto suffered a landslide defeat in Pakistan's national election, according to unofficial returns today.

Preliminary results in Wednesday's balloting showed Bhutto's Pakistan People's Party (PPP) badly trailing its rightist opponents, the Islamic Democratic Alliance, or IJI from its Urdu-language initials. The ousted prime minister was beaten in one of two national assembly contests she entered, although she was elected overwhelmingly from her home district of Larkana.

With results reported in 136 of the country's 217 assembly contests, the IJI coalition led by industrialist Nawaz Sharif had captured 68 seats to 26 for the PPP and appeared comfortably positioned to win a majority in parliament. A tribal party allied with the IJI picked up six seats, while the remaining seats were divided among ethnic and religious parties, most of them expected to join the IJI.

Bhutto charged that the vote had been stolen by her opponents. "There has been massive rigging. . . . Pakistan is going to be faced with deeper crisis, and I see civil unrest," she said. Bhutto added, however, that she wanted to "play a constructive role" in building democracy in Pakistan.

Several hours after the polls closed, independent observers gave mixed report about the election's fairness, but there appeared to be little immediate evidence of massive vote fraud. Scattered instances of irregularities were reported, including charges that voters favoring the PPP were turned away from polling places and that force was used to seize several ballot boxes.

Reporters visiting a polling stations in hotly contested Punjab province found relatively few complaints about abuses or irregularities, however. Polling agents from the PPP and IJI monitored balloting throughout the day, and those interviewed said the voting had been generally satisfactory.

Members of a U.S.-led multinational observer team declined comment Wednesday night, saying they would not make public their findings about the election until Friday.

Bhutto has leveled complaints of rigging throughout the campaign, which began after her government was dismissed Aug. 6 amid corruption charges in a move backed by the military. After her ouster, an IJI-led caretaker government brought corruption charges against Bhutto, her husband Asif Ali Zardari, and members of the PPP government.

PPP leaders said the charges were part of a campaign to keep them out of power. A public perception that the IJI-led interim government had handled the cases involving Bhutto unfairly appeared to provide momentum to her campaign. Bhutto's husband, who was jailed this month on kidnapping and extortion charges, won an assembly seat from Karachi, but was defeated in a second contest in Sind province.

The IJI swept populous Punjab, which had been viewed as a key electoral battleground. Sharif defeated his PPP-allied opponents in two contests, winning in Lahore by about 20,000 votes. In that contest, the PPP candidate, retired air marshal Asghar Khan, denounced the result as fraudulent.

Bhutto was soundly beaten in a Peshawar assembly contest she had been favored to win. Ghulam Ahmed Bilour, a tribal leader with the Awami National Party (ANP), garnered 51,188 votes to 38,695 for Bhutto. But the former prime minster trounced her opponent in Larkana, 94,209 votes to 714

The IJI coalition is considered likely to form a government led either by Sharif or by interim Prime Minster Ghulam Mustafa Jatoi, who also won a decisive victory in his home district in Sind. Sharif said Wednesday night that the IJI was well-positioned to "form a strong government . . . bringing {Pakistan} out of economic backwardness and ushering in an era of industrial and agricultural revolution."

The vote apparently heralds the return to power of a number of Pakistani politicians associated with the martial law rule of the late general Mohammed Zia ul-Haq, who ordered the hanging of Bhutto's father after leading a 1977 military coup. Ejaz ul-Haq, Zia's son, won solidly in two assembly contests and afterward led supporters to Zia's Islamabad grave for a prayer ceremony.

While there were signs several weeks ago that the caretaker government's perceived vindictiveness toward Bhutto and her family had swung momentum in the PPP's favor, more recently IJI leaders took the offensive, accusing Bhhutto of engineering American interference in Pakistani affairs and jeopardizing the country's sovereignty.

At rallies, the IJI leaders cited letters of support for Bhutto written by U.S. members of Congress after her government's dismissal in August. Coalition leaders also sharply criticized a letter signed by 53 U.S. senators urging that free and fair elections be held and that Bhutto be allowed to participate.

In interviews in northern Punjab Wednesday, voters openly expressed resentment at perceived U.S. interference in the election campaign.

Bhutto told reporters in Larkana that she feared a victory by the IJI would lead to renewed persecution of her family and her supporters. "I know that if they keep the numbers {of PPP seats} down . . . then they will go for the jugular -- me, my husband, my party," she said.

It was not clear early this morning how far Bhutto would go in pressing her charges about vote rigging or whether her allegations are likely to receive backing from international election observers or her supporters in the West.

The observer team's findings are likely to affect an estimated $600 million in annual U.S. aid to Pakistan. The aid was suspended this month because of concern over Pakistan's nuclear program.

Bhutto charged that a large number of PPP election workers had been kidnapped in parts of rural Sind where close contests were expected. Defeats for the PPP were reported across the country, however.

The caretaker government's national election commissioner, whom the PPP has accused of partisanship, said Wednesday night that he had received fewer complaints about irregularities than during the last election in 1988, when Bhutto won a plurality and eventually formed a coalition government.

Several people were reportedly killed in rural Sind and in the North West Frontier Province in shootings linked to the election. Balloting in one national assembly district was suspended after the IJI candidate was assassinated Tuesday by unidentified gunmen.

In Lahore, PPP-allied candidate Khan charged that IJI election workers had entered a polling station, removed voting materials and stuffed voting boxes with IJI ballots. There was no independent confirmation of Khan's charge, but the U.S.-led observer team was said to be investigating the incident.

Western reporters traveling in rural Punjab said some women voters alleged they had been barred from polling stations because they intended to vote for the PPP. But these reporters said they observed no sign of large-scale rigging.

In the northern Punjab city of Rawalpindi, the PPP had identified two hard-fought contests where it expected rigging to occur. Visits to polling places in the city and interviews with about a dozen election officials Wednesday turned up no significant complaints. Polling agents for both the PPP and the IJI said they were satisfied with the conduct of the voting.