A boy with a bicycle, wearing a cap of India's main opposition Bharatiya Janata Party (BJP) is seen, ahead of the second phase of the general election at Muzaffarnagar in the northern Indian state of Uttar Pradesh April 9, 2014. Around 815 million people have registered to vote in the world's biggest election - a number exceeding the population of Europe and a world record - and results of the mammoth exercise, which concludes on May 12, are due on May 16. [Photo/Agencies]

NEW DELHI - Hundreds of millions of Indian voters go to the polls in a key phase of general elections on Thursday, with the fate of ruling Congress and opposition Bharatiya Janata Party (BJP) greatly decided in the current round of polling in the capital Delhi and the biggest state Uttar Pradesh.

After the preliminary polling in the northeast region, India will see 91 out of 543 seats in the Lok Sabha (Lower House of Parliament) being contested Thursday in Delhi, Haryana and Kerala and several in Uttar Pradesh, Bihar, Orissa and Maharashtra.

While opinion polls say the BJP has a good chance to win over the Congress in Delhi, Haryana, western Uttar Pradesh, south Bihar and eastern Maharashtra, the party could face stiff resistance in some major pockets there.

"A surge would be critical to BJP reaching its target of 200- plus Lok Sabha seats, which would require a 70-80 percent strike rate in this round," said Times of India online.

The Congress would try to keep some of its seats in Delhi, Haryana and Uttar Pradesh to weaken the "Modi effect". In the local polls last December, the BJP won narrowly in Delhi but the Congress backed anti-graft Aam Aadmi party, which won second most votes, to set up a short-lived coalition government.

A tough battle is also predicted for the BJP in Bihar, where its former ally, chief minister Nitish Kumar is a fierce personal rival of BJP's prime ministerial candidate Narendra Modi, who has tried hard to win support in the state. His campaign also came under bomb attacks last October in Bihar by suspected Muslim militants.

In Uttar Pradesh, where the BJP nominated all its heavy weights in its constituencies, local parties Samajwadi Party, BSP and some other smaller parties, apart from the Congress all have respective strongholds and vote banks. These parties are also seeking support of the state's strong Muslim community and taking advantage of the effects of last year's communal violence in Muzzaffanagar in the state, where dozens were killed and thousands displaced.

The general election started on Monday and will go on for one month in nine phases.