Polls opened on Monday for the crucial fifth phase of India's marathon elections including in two constituencies in the vote-rich state of Uttar Pradesh, where opposition Congress party president Rahul Gandhi and his mother Sonia Gandhi hope to retain their seats.

Voting began amid scorching summer temperatures and tight security in Uttar Pradesh in northern India, where more than 25 million people are registered to cast ballots for 14 members of India's Parliament.

Rahul Gandhi is seeking re-election for a fourth consecutive time in Amethi. He's the son of assassinated former Prime Minister Rajiv Gandhi. Rajiv Gandhi's widow, Sonia Gandhi, is running from neighboring Rae Bareli. Both constituencies are considered Congress party bastions.

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.

The polling, spread over 51 constituencies spread over seven states, also is taking place in his mother Sonia Gandhi's constituency of Rae Bareli. Modi's Hindu nationalist party is trying hard to defeat the top Congress leadership both in Amethi and Rael Bareli to gain ascendancy for years to come.

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 distress of farmers aggravated by low crop prices. They have also made alleged corruption in a deal to purchase French fighter jets as one of the major election issues.

Monday's polling will mark the completion of voting in more than 400 out of 543 parliamentary seats. The 39-day process will be completed on May 19. The counting will be held on May 23.

The election's fifth phase is a war of titans.

Rahul Gandhi is pitted against the government's textile minister, Smriti Irani, for Amethi.

Irani lost to Gandhi in 2014 polls but in the last five years has steered central government funds for development to the constituency and visited often.

“This time BJP is going to win the election,” Irani told The Associated Press.

“They 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.”

Gandhi is also contesting the election from Wayanad, a district in the southern state of Kerala. In India, it's possible to stand for more than one constituency, but one can represent only one seat in Parliament.

His sister Priyanka Gandhi Vadra, who is also the national general secretary of the party, carried out intensive campaigns in both Amethi and Rae Bareli, and predicted that her brother would carry Amethi by an even larger margin in this year's polls.

“There is an emotional attachment between the people of Amethi and Congress,” she said.

In other races, the central government's powerful Home Minister Rajnath Singh is in the fray from Lucknow, the capital of Uttar Pradesh. Another Modi government minister, Menaka Gandhi, who has strained relations with her sister-in-law Sonia Gandhi, is contesting from Sultanpur.

State chief electoral officer Venketshwar Lu told reporters on Monday that polling started smoothly and that shade, fans and drinking water had been made available at all polling booths.

“We are expecting good turnout this time,” he said.