Thursday's first phase of voting is centred on northern and eastern India, including areas beset by a range of violent conflicts involving tribal, Maoist and Muslim fighters.

More than two million security personnel have been deployed around the country until balloting ends on May 13.

Voter issues

Many of India's voters are expected to make their choices along religious and caste lines or on the basis of strictly regional issue

A survey published in the Hindustan Times on Tuesday said development and economic opportunities were among the main issues for the voters in this election.

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The Congress, ending a five-year period in power, has seen its main achievement - economic growth averaging more than eight per cent in recent years - hit by the global economic crisis.

In Amethi, a rural constituency represented by Rahul Gandhi, the son of Sonia Gandhi, the Congress chief, voters lament the lack of basic facilities like electricity, water and roads.

In contrast, the glittering shopping malls in India's bustling cities show that those who have benefitted most from India's economic reforms are a growing urban middle class, while millions of poor are being left behind.

Analysts say political parties are doing a poor job addressing the real concerns of the people.

"Sadly, there is no party that really is talking about basic issues like education, health, energy, housing, employment," Dipankar Gupta, an analyst in New Delhi, said.

"Or even thinking in terms of regenerating our economy, which has you know fallen to rather bad times."

Candidates' confrontation

The election campaign is also focusing on the confrontation between the two prime-ministerial candidates of this election - Manmohan Singh of the Congress and LK Advani of the BJP.

Incumbent Manmohan is 76-years-old and Advani is 81.

Advani has publicly accused Singh of being a weak prime minister, saying that "he has devalued this post".

The normally mild-mannered Singh has also criticised Advani, recalling his role in the controversial demolition of a mosque in 1992 and the anti-Muslim riots that occurred when the party was last in power.

In depth

Voting takes place in 543 constituencies in five phases from April 16 to May 13. Results declared on May 16.

Phase I
16 April: Andhra Pradesh, Arunachal Pradesh, Assam, Bihar, Jammu and Kashmir, Kerala, Maharashtra, Manipur, Meghalaya, Mizoram, Nagaland, Orissa, Uttar Pradesh, Chattisgarh, Jharkhand, Andaman and Nicobar Islands, Lakshadwep

Total constituencies: 124

Phase II
22 April: Manipur
23 April: Andhra Pradesh, Assam, Bihar, Goa, Jammu and Kashmir, Karnataka, Madhya Pradesh, Maharashtra, Orissa, Tripura, Utter Pradesh, Jharkhand

Total constituencies: 141

Phase III
30 April: Bihar, Karnataka, Madhya Pradesh, Maharashtra, Uttar Pradesh, West Bengal, Jammu and Kashmir, Gujarat, Sikkim, Dadar and Nagar Haveli, Daman and Diu

Total constituencies: 107

Phase IV
7 May: Bihar, Haryana, Jammu and Kashmir, Punjab, Rajasthan, Uttar Pradesh, West Bengal, Delhi

Total constituencies: 85

Phase V
13 May: Himachal Pradesh, Jammu and Kashmir, Punjab, Tamil Nadu, West Bengal, Uttarakhand, Chandigarh, Pondicherry, Uttar Pradesh

Total constituencies: 86

Singh, an Oxford-educated economist, was picked by Gandhi to be prime minister after the 2004 elections.

Polls indicate neither the Congress nor the BJP will win enough seats in the 543-seat Lok Sabha, or lower house of parliament, to rule on their own.

This has opened the door for regional parties focused on local issues or caste politics, to try and stake a claim to some of the support traditionally given to the two national parties.

The prospect of a shaky coalition of disparate allies is a turn-off for most Indian voters, with any new government likely to face national security concerns and a sharp economic slowdown after years of soaring growth.

The only viable alternative to a Congress- or BJP-led coalition is provided by a loose alliance of left-leaning and regional parties called the Third Front.

Negotiations are ongoing, but the alliance may join forces with Mayawati, a self-styled champion of the lower castes who has made no secret of her ambition to become India's first "untouchable" prime minister.

Barnaby Phillips, Al Jazeera's correspondent in Kerala, said: "Certainly as far as Congress is concerned, the left are saying, no, they will not work with them.

"They have that disagreement of principle as far as they are concerned over India's deal of nuclear cooperation with the United States. And that's when they stopped working with the Congress-led coalition," he said.

"Having said that, politics is politics. Neither Congress or the BJP is likely to emerge from this election, barring a major shock, with a clear majority.

"Either one of those parties it would appear is going to be looking around for coalition partners. And at that stage, who's to say.

"The left itself is very fractured and I've no doubt that there will be some people within it who would be tempted by a return to power if that were on offer."

Results of the election, which will use more than 1.3 million electronic voting machines in 828,804 polling stations, are expected on May 16.