Millions of Indians cast ballots under unprecedented security Monday amid predictions that voters would give former Prime Minister Rajiv Gandhi a solid victory but deny his center-left Congress Party an absolute majority in Parliament.

The first day of history's largest elections, in which 514 million people are eligible to vote, was marred by riots and clashes between supporters of rival parties that left at least 30 people dead and scores injured, officials and news reports said.The balloting is staggered over three days to ensure adequate security, and voting continues in other parts of the country Thursday and Sunday. Vote counting begins May 27.

Turnout was moderate during polling from 7 a.m. to 5 p.m. Election officials said turnout appeared to be lower than usual, with 55 percent of the electorate casting ballots. Observers said the searing heat may have kept many away.

Election officials said 1.5 million police were on duty along with thousands of paramilitary troops after more than 110 people died in pre-election unrest.

Despite the security, officials and news reports said 30 people were killed and about 90 were wounded in northern Bihar and Uttar Pradesh states.