NEW DELHI — A top opponent of Indian Prime Minister Narendra Modi vowed to keep fighting "dictatorship" before he returned to jail on Sunday, following elections widely expected to produce another landslide victory for the Hindu-nationalist leader.

Arvind Kejriwal is among several opposition leaders under criminal investigation, with colleagues describing his arrest the month before the general elections began in April as a "political conspiracy" orchestrated by Modi's ruling Bharatiya Janata Party (BJP).

The chief minister of the capital Delhi and a key leader in an alliance formed to compete against Modi, Kejriwal was detained in March over a long-running corruption probe.

He was later released and allowed to campaign but was ordered to return to jail once voting ended.

"When power becomes dictatorship, then jail becomes a responsibility," said Kejriwal, who promised to continue "fighting" from behind bars.

"I don't know when I will return," he told supporters in an emotional departure speech at his Aam Aadmi Party headquarters. "I don't know what they will do to me... every drop of my blood is for the country."

Kejriwal later returned to jail, his party spokesman told Agence France-Presse (AFP).

Exit polls showed Modi was well on track to triumph, with the premier saying he was confident that "the people of India have voted in record numbers" to reelect his government.

Results are expected on Tuesday, but supporters of Modi in his constituency of Varanasi — the northern Indian city that is the spiritual capital of the Hindu faith — said they believed their leader's win was secure.

Voting in the seventh and final staggered round of the six-week poll ended on Saturday, held in brutally hot conditions across swaths of the South Asian country.

At least 33 polling staff died from heatstroke in northern Uttar Pradesh state alone, where temperatures hit 46.9 degrees Celsius (116.4 degrees Fahrenheit), election officials said.

India's top court granted Kejriwal bail last month, giving a fleeting boost to the opposition's quixotic campaign to oust Modi, but ordered him to return to custody after the election.

Kejriwal, 55, has been chief minister for nearly a decade and first came to office as a staunch anti-corruption crusader.

His government was accused of corruption when it implemented a policy to liberalize the sale of liquor in 2021 and give up a lucrative government stake in the sector.

The policy was withdrawn the following year, but the resulting probe into the alleged corrupt allocation of licenses has since led to the jailing of two top Kejriwal allies.

"All of you, take care of yourselves," Kejriwal, who has consistently denied wrongdoing and refused to relinquish his post, said earlier on social media. "I will take care of you all in jail."

Modi's political opponents and international rights groups have long sounded the alarm about threats to India's democracy.

United States think tank Freedom House said this year the BJP had "increasingly used government institutions to target political opponents."

Rahul Gandhi, the most prominent member of the opposition Indian National Congress party and scion of a dynasty that dominated Indian politics for decades, was convicted of criminal libel last year after a complaint by a member of Modi's party.

His two-year prison sentence saw him disqualified from parliament until the verdict was suspended by a higher court and raised concerns over democratic norms in the world's most populous country.

Hemant Soren, the former chief minister of the eastern state of Jharkhand, was also arrested in February in a separate corruption probe.

Kejriwal, Rahul Gandhi and Soren are all members of an opposition alliance composed of more than two dozen parties, but the bloc struggled to make inroads against Modi.