India's Prime Minister Narendra Modi waves to his supporters during a roadshow in Puri district of the eastern state of Odisha, India, on Monday. Reuters

Millions of Indians across 49 constituencies began casting ballots on Monday as the country’s six-week-long election enters its final stages.

Monday’s polling in the fifth round of multi-phase national elections across six states and two union territories is crucial for Prime Minister Narendra Modi’s ruling Bharatiya Janata Party as it includes some of its strongholds in states like Uttar Pradesh and West Bengal.

The staggered election will run until June 1 and nearly 970 million eligible voters, more than 10% of the world’s population, will elect 543 members to the lower house of Parliament for five years. The votes are scheduled to be counted on June 4.

With two more phases of polling left, overall voter turnout has been lower than in previous elections. Some poll experts have suggested that some of Modi’s party core supporters were staying away.

People queue up to vote outside a polling booth in Howrah, India, on Monday. AP

Most polls show Modi and his party leading in the race for seats in the lower house of Parliament over their main challenger, a broad opposition alliance led by the Indian National Congress and powerful regional parties. However, it faces stiff resistance from the opposition, which appears to have tapped into discontent against Modi's government.

Monday’s polling will also see opposition leader Rahul Gandhi, the scion of the Gandhi-Nehru dynasty, running for office from Rae Bareli constituency in Uttar Pradesh state.

Gandhi also ran for office from Wayanad in southern India, which has already voted. India allows candidates to contest multiple constituencies but they can represent only one.

Indian PM Modi on Monday led a two km long roadshow in the holy town of Puri in Odisha.

Voters queue up to cast their ballots at a polling station in Mumbai on Monday. AFP

PM Modi after arriving at the Talabania helipad in Puri went to the Shree Jagannath Temple in a carcade to have a 'darshan' of the holy triad. He later embarked on a huge roadshow from Marchikote Chowk to the Medical Square.

The Prime Minister waved and greeted thousands of enthusiastic crowds gathered on both sides of the ‘Badadanda’ (Grand Road of Puri). The admirers as well as the Bharatiya Janata Party workers also greeted PM Modi with ‘Modi Modi’, Bharat Mata Ki Jay and Jay Shree Ram slogans as the PM's vehicle moved past.

More than 100 saffron-clad women BJP workers walked ahead of PM Modi's vehicle during the roadshow. Traditional artists were seen performing various cultural programmes on the Grand Road during the roadshow.

BJP’s Puri Lok Sabha candidate Sambit Patra and state president Manmohan Samal accompanied PM Modi on his vehicle during the roadshow.

Policemen stand guard as people arrive to vote in Ayodhya, India, on Monday. AP

PM Modi later flew to Angul where he is scheduled to address a huge public gathering. The Prime Minister will address another public meeting at Cuttack Bali Jatra field later in the day.

Meanwhile, the fifth phase of polling is underway in five parliamentary seats -- Bargarh, Sundargarh, Bolangir, Kandhamal, Aska and also 35 Assembly seats of the state on Monday.

The Assembly and Lok Sabha elections are being held simultaneously in Odisha in four phases from May 13 to June 1. The results of the polling for both Lok Sabha and Vidhan Sabha will be out on June 4.

Agencies