More than 25 million people were registered to vote for 14 members of India's Parliament in Uttar Pradesh state in northern India, where temperatures were scorching and security was tight.
The Election Commission said turnout was 57.1% in Uttar Pradesh and averaged of 62.5% in the 51 constituencies in seven states where the polling was held. More voting rounds happen on May 12 and May 19 and voting from all rounds will be counted on May 23.
Rahul Gandhi is seeking re-election for a fourth consecutive time in the Uttar Pradesh town of Amethi. He is the son of assassinated former Prime Minister Rajiv Gandhi. Rajiv Gandhi's widow, Sonia Gandhi, is running in the community of Rae Bareli near Amethi.
Both constituencies are considered Congress party bastions.
Police said suspected insurgents attacked two polling stations with bombs in the Pulwama area of Indian-controlled Kashmir. One exploded without causing injuries and the second did not explode and was defused by security forces, police said.
In West Bengal state, members of the Hindu nationalist Bharatiya Janata Party and party workers with the powerful regional Trinamool Congress party hurled crude bombs at each other, the Press Trust of India news agency said.
Government forces used canes to disperse them, injuring some people in the constituencies of Bangaon, Barrackpore, Hooghly and Howrah, Press Trust reported.
India's multi-phase elections, which started April 11 and last five weeks, are seen as a referendum on Prime Minister Narendra Modi and his Hindu nationalist Bharatiya Janata Party, which controls Uttar Pradesh.
Voting for one parliamentary seat in Indian-controlled Kashmir is being spread over three days because of security threats posed by almost daily clashes, government crackdowns and anti-India protests.
Muslim separatists have said the vote is an illegitimate exercise under India's military occupation and Kashmir turnout was extremely low. As the voting ended, anti-India protesters clashed with security forces in several places, leaving some people injured, police said.
Kashmiri youths hurled stones at election staff and their security guards as they moved into schools and government buildings Sunday night to set up polling stations in the area. Troops fired shotguns and tear gas to quell the anti-India protests that injured people, police said.
Voting also was held in the remote mountainous Ladakh region, which has India's highest polling station at an altitude of 15,000 feet (4,570 meters). Another high-altitude polling station was set up for just 12 voters from the cold desert region.
Modi has adopted a nationalist pitch in trying to win votes from the country's Hindu majority by projecting a tough stance against Pakistan, India's Muslim-majority neighbor and archrival.
The opposition is challenging him over India's 6.1% unemployment rate — the highest in years — and the economic difficulties of farmers hurt by low crop prices. Opposition officials have also alleged there was corruption in a deal for India to purchase French fighter jets, one of the election's major issues.
Monday's polling marked the end of voting for more than 400 out of 543 parliamentary seats. The 39-day process will be completed on May 19 and votes will be counted on May 23.
In the most prominent race, Rahul Gandhi is running against the government's textile minister, Smriti Irani.
Irani lost to Gandhi in 2014 but over the last five years has steered central government funding for development in Amethi and has visited the town frequently.
Gandhi and his party "promised the moon to these people but in reality Amethi is one of the most neglected constituencies because Gandhis never took interest in development of this region," Irani told The Associated Press in an interview.
Gandhi is also contesting the election from Wayanad, a district in the southern state of Kerala. In India, it's possible to run in more than one constituency, but one can represent only one seat in Parliament.
His sister, Priyanka Gandhi Vadra, who is also national general secretary of the party, campaigned intensely for him in both constituencies.
"There is an emotional attachment between the people of Amethi and Congress," she said.
In other races, powerful Home Minister Rajnath Singh is running in Lucknow, the state capital of Uttar Pradesh. Another Modi government minister, Menaka Gandhi, who has strained relations with her sister-in-law Sonia Gandhi, is contesting from the Uttar Pradesh city of Sultanpur.
State chief electoral officer Venketshwar Lu told reporters on Monday that polling started smoothly and that shade, fans and drinking water was available at all polling stations.
This story has corrected the spelling of Priyanka Gandhi Vadra.