AHMEDABAD: Millions voted on Thursday in India's Gujarat state where Hindu nationalist Narendra Modi is seeking a big win to spur his prime ministerial ambitions, 10 years after religious riots on his watch.

Crowds ignored the December chill to head to polling stations in the first of two rounds of voting in the western coastal state, one of the fastest developing regions of India that has been run by chief minister Modi since 2001.

“A vote is foundation of a strong and vibrant democracy,” the 62-year-old wrote on his Twitter account.

Election watchdog officials said almost 3.5 million people out of the 38-million-strong electorate had cast their ballots in the first three hours.

Modi, who has secured thumping victories in the last two polls, is looking to secure another sizeable majority for the Bharatiya Janata Party (BJP) to bolster his reputation, which was stained by religious riots in Gujarat in 2002.

Though he has never declared his ambition to be prime minister, his desire for the top spot in his party is an open secret and he is widely thought to be angling to lead the BJP into national elections due in 2014.

His main rival in Gujarat is the left-leaning Congress party, which runs the federal government and is dominated by the Gandhi dynasty which has run India for most of its post-independence history.

Rahul Gandhi, the next-in-line who might face Modi in the 2014 national polls, has campaigned locally where he accused his rival of being autocratic and ignoring the poor in the home state of late independence hero Mahatma Gandhi.

“He wants to hear only his own voice. He has his dream and he thinks only about his own dream,” Gandhi told supporters on Tuesday.

The final phase of the balloting is scheduled for Dec 17 with counting to take place three days later.

Some 100,000 security personnel including federal troopers are on duty at around 45,000 polling stations – some 17,000 of them labelled “vulnerable” to violence, the state home department said.

Modi's links to some of the worst sectarian violence in post-independence India make him a hate-figure for many Muslims and secularists and his rise to the top of the BJP would be controversial.

On Wednesday, he was back in the headlines after claiming the federal government was set to “hand over” a disputed strip of water in Gujarat to neighbour Pakistan.

“I would earnestly request you to stop this dialogue with Pakistan at once and Sir Creek should not be handed over to Pakistan,” Modi wrote in a letter to Prime Minister Manmohan Singh, released by his party.

Singh, who has pushed a peace dialogue with Pakistan as a means to reduce tension in nuclear-armed South Asia, countered that the letter was a “mischievous” and “baseless” stunt ahead of the election.

Modi is blamed by rights groups for turning a blind eye to the violence in Gujarat in 2002 which saw as many as 2,000 people, mostly Muslims, killed.

The son of a foodstall owner, who rose through the ranks of hardline grassroots Hindu groups, Modi has always denied any wrongdoing in the riots and has never been convicted over the violence.

“Gujarat is progressing because we have peace, unity and compassion here,” Modi told AFP in an interview in October.

On the campaign trail, he has targeted the corruption-plagued federal government Delhi and the heads of the ruling Congress party, particularly the Italian-born leader Sonia Gandhi, who he portrays as out-of-touch and foreign.

A string of interviews with the foreign media has helped raise chief minister Modi's profile abroad, while his embrace of Twitter and Youtube has widened his appeal to Gujarat's overwhelmingly young electorate.