Brisk polling was reported on Thursday across the 20 Lok Sabha seats in Kerala, with over 21% of the electorate casting their ballots within three hours.
Kannur topped the voting with 24%, while over 19% ballots were polled in the capital, according to the Kerala chief electoral officer's website.
In the 2009 election, the first hour of polling recorded a mere 4% votes.
Chief Minister Oommen Chandy and his family cast their votes in Puthupally in Kottayam.
Chandy later told reporters he was confident that the electorate would give his government a "good victory" on account of its performance.
"Now that the process has begun, I do not wish to speculate on what our tally would be. But I can tell you one thing, there seems to be a very positive vibe towards our candidates and we will come out with flying colours," said Chandy.
Defence Minister A.K. Antony and his family cast their votes in a booth near their home in the Kerala capital.
"This time, the UDF will get more seats than the previous poll. And this time too, the BJP will not open its account in Kerala," Antony said.
In the outgoing Lok Sabha, the Congress-led United Democratic Front had 16 seats, while the CPI-M-led Left Democratic Front had four. The BJP is yet to open its Lok Sabha account in Kerala, and the party also does not have any presence in the 140-member state assembly.
Enthusiasm to cast votes was evident across the state, as people started to queue up much before polling began at 7 am.
Coastal areas, especially the state capital district and Alappuzha, saw huge crowds.
As many as 55 companies of security personnel drawn from outside the state have been deployed across Kerala.
CPI-M state secretary Pinnarayi Vijayan said people will teach the UDF a lesson this time, and claimed the sentiment was evident from the manner in which the electorate turned up in large numbers.
Election officials have identified 10% of the total 21,424 polling booths as critical - most of them are in Kannur, Kozhikode and Kasargode districts.
In 2009, Kerala recorded 73.37% voter turnout.
Kerala's 24.2 million strong electorate has to choose representatives from 242 male candidates and 27 female candidates.