Prime Minister Atal Bihari Vajpayee's Hindu nationalist Bharatiya Janata Party has won a comfortable majority in India's parliamentary elections.

The decisive outcome promises the nation a period of political stability for which it has long yearned, and it solidifies the evolution of Vajpayee's BJP into a mass political movement after years of being viewed as a fringe religious group.

With official results from five weeks of balloting almost complete, the BJP and its allies in the 24-party National Democratic Alliance won 284 of 543 seats in the lower house of Parliament, the Lok Sabha, while the opposition Congress party and its allies won 130. Leftist parties and others accounted for 99 seats and, as of late tonight, the winners of 30 seats had not been determined.

Vajpayee's solid victory came as a relief to many Indians who feared that a close result in the third national election in four years would leave the country with another narrowly based government distracted by political horse-trading and instability at a time of high regional tensions over Kashmir and international controversy over India's nuclear weapons program.

India and Pakistan have tested nuclear weapons and missiles capable of delivering them within the past 18 months, and the two countries fought in a 10-week border conflict this summer in the mountains of Kashmir, a Himalayan region that both have claimed.

Vajpayee appears eager to return to negotiations with Pakistan that he initiated last winter, suggesting his re-election may lead to reduced tensions with Islamabad, despite the Kashmir dispute. At the same time, advisers in Vajpayee's outgoing government have outlined a defense doctrine that makes it clear the country intends to equip itself with nuclear weapons so it can retaliate swiftly against any nuclear attack.

"We have been voted back to power to continue the good governance that Vajpayee has been giving to the people of this country," BJP spokesman Venkaiah Naidu told journalists. The voters' verdict, he said, is a mandate "for the continuance of good governance" and "against the destabilizers" in Congress and other parties that brought down the Vajpayee government in April by a one-vote margin.

Congress party leader Sonia Gandhi issued a statement saying her party will "accept unhesitatingly the verdict of the people." She said the election result "calls for introspection, frank assessment and determined action." The 53-year-old Gandhi, the widow of assassinated prime minister Rajiv Gandhi, took the party reins last summer in what turns out to have been an unsuccessful attempt to revive its fortunes.

A relaxed and triumphant Vajpayee, 76, spent today telephoning political allies and inviting them to join his new government. Party leaders later this week are expected to chose Vajpayee, the longtime BJP head, as prime minister. Parliament is scheduled to take office Oct. 21.

"For the first time in 27 years in India, an incumbent prime minister has been returned to office; that's remarkable," Foreign Minister Jaswant Singh said tonight. The others have been defeated, assassinated or were otherwise unable to complete their terms.

The election was a major logistical feat, with more than 650 million voters going to the polls in 90,000 locations. The voting was staggered over five weekends to improve security and reduce fraud. In several states, however, the polling was marred by serious violence, mostly attacks by separatist and leftist guerrilla groups.

In contrast to the BJP's victorious glow, Congress party officials had to face a day of bitter defeat and internal recrimination. Some party leaders were already blaming Gandhi, the shy heiress to India's political dynasty, for having failed her party and her country.

"It is a great disappointment for us," said Kapil Sibil, a Congress spokesman. "It is now clear that the Congress position will not be better than it was in the last Lok Sabha. We will lose some seats. We have to think deeply and look for the reasons for not performing better and prepare ourselves for the next round. There is no question of blaming anybody for this."

Gandhi, a reluctant campaigner, ran for office in two parliamentary districts, as allowed by Indian law. She won in both, and aides said she plans to represent one and choose a Congress colleague to represent the other.

Vajpayee, a popular leader known for his moderate views, has helped to make the BJP palatable to non-Hindus and other Indians, and he won the single parliamentary seat for which he ran. The ruling alliance was also helped by India's triumph last summer in the conflict with Pakistan-based guerrillas and troops in the Kargil mountains of Kashmir.

The new ruling alliance includes a large number of regional parties, giving it a heterogenous flavor that reflects India's diversity. Some independent analysts cautioned, however, that this could cause difficulties not unlike those Vajpayee encountered in his prior term, which lasted 13 months. The defection of several regional leaders from his camp helped precipitate the crisis that led to the government's collapse in April.

"With so many alliances, it may be easy to form the government, but it will not be so easy to run and manage the government," said Mahesh Rangarajan, a political analyst.

Vajpayee and Gandhi both campaigned on platforms that stressed political stability and harmony. But voters appeared to punish Congress for bringing down the government last spring without being able to form an alternative. Some also were unable to accept Gandhi as prime minister because she was born in Italy, even though she has lived here for 30 years.

Special correspondent Rama Lakshmi contributed to this report.