Millions of Indians have voted in the penultimate round of a gruelling national election, with a combined opposition trying to stop Prime Minister Narendra Modi from winning a rare third consecutive term.

Many people lined polling stations before the start of voting at 7am (01:30 GMT) on Saturday to avoid the blazing sun later in the day at the peak of summer.

The temperature soared to 43 degrees Celsius (109.4 degrees Fahrenheit) in the afternoon in capital New Delhi. India’s weather bureau this week issued a heatwave “red alert” for the city and surrounding states where tens of millions of people cast their ballots.

Lakshmi Bansal, a housewife, said while the weather was hot, people usually went out to shop and even attended festivals in such heat.

“This [election] is also like a festival, so I don’t have a problem voting in the heat,” Bansal said.

Nearly 970 million voters – more than 10 percent of the world’s population – were eligible to elect 543 members to the lower house of parliament for five years.

Saturday’s voting in 58 constituencies, including seven in New Delhi, completed polling for 89.5 percent of 543 seats in the lower house of parliament.

The voting for the remaining 57 seats on June 1 will wrap up the six-week election. The votes will be counted on June 4.

President Droupadi Murmu and External Affairs Minister S Jaishankar were among the early voters. Opposition Congress party leaders, Sonia Gandhi and her son Rahul Gandhi, also voted in New Delhi.

Mehbooba Mufti, a former chief minister of Indian-administered Kashmir, held a protest with her supporters on Saturday, claiming that scores of her party workers were detained by the police to prevent them from voting. Mufti, the chief of the People’s Democratic Party who is contesting the parliamentary election in the Anantnag-Rajouri district, said she complained to election officials.

In West Bengal state, workers belonging to the All India Trinamool Congress party, blocked the car of Agnimitra Paul, one of Modi’s Bharatiya Janata Party (BJP) candidates, as she proceeded to vote in the Medinipur constituency. The two parties are rivals in the state and their workers often clash on the streets.

‘Opposition doing better than expected’

This election is considered one of the most consequential in India’s history and will test Modi’s political dominance. If Modi wins, he will be only the second Indian leader to retain power for a third term, after Jawaharlal Nehru, the country’s first prime minister.

Modi ran his campaign like a presidential race, a referendum on his 10 years of rule. He claimed to help the poorest with charity, free healthcare, providing toilets in their homes, and helping women get free or cheap cooking gas cylinders.

But Modi changed tack after a poor turnout of voters in the first round of the election and began stirring Hindu nationalism by accusing the Congress party of pandering to minority Muslims for votes.

Hindus account for 80 percent, and Muslims nearly 14 percent, of India’s over 1.4 billion people.

“When the polls began it felt like a one-horse race, with Modi leading from the front. But now we are seeing some kind of shift,” political analyst Rasheed Kidwai said.

“The opposition is doing better than expected and it appears that Modi’s party is rattled. That’s the reason you see Modi ramping up anti-Muslim rhetoric to polarise voters.”

‘Vote against dictatorship’

Analyst Kidwai said the opposition has challenged Modi by centring its campaign narrative on social justice and rising unemployment, making the contest closer than expected.

Among the prominent opponents is Delhi Chief Minister Arvind Kejriwal, 55, leader of the opposition Aam Aadmi Party (AAP).

“Please vote, use your right to vote, and vote against dictatorship,” Kejriwal said after casting his vote.

Kejriwal was arrested in March in a long-running corruption case and jailed for several weeks before the Supreme Court granted him bail earlier this month and he returned to the campaign trail.

Investigators “had no proof and yet they jailed him”, opposition voter Yogesh Kumar, 42, told the AFP news agency. “This is a blunt show of power.”

Kejriwal’s jailing actually benefitted the AAP, Neelanjan Sircar of the Centre for Policy Research, told Al Jazeera.

“When people saw Arvind Kejriwal was arrested, they believe the BJP was actually jailing someone who is legitimate opposition,” Sircar said. “This jailing of Kejriwal convinced the BJP how popular he actually is.”

Modi’s political opponents and international rights campaigners have long sounded the alarm on India’s shrinking democratic space.

US think tank Freedom House said this year that the BJP had “increasingly used government institutions to target political opponents”.