An estimated 45 to 50 per cent of the 2.32 crore electorate cast their ballots in the final phase of Lok Sabha elections for 17 constituencies in Madhya Pradesh, which witnessed sporadic violence, rigging and damage to Electronic Voting Machines.

"We expect the voting to reach halfway mark in this final phase," sources in the state election office said in Bhopal on Monday adding that reports of violence and rigging were being ascertained.

In an alleged rigging incident in Bhind Lok Sabha constituency, at least 18 people, including son of BJP MP Ramlakhan Singh, were arrested for casting a few bogus votes by intimidating polling staff, police said.

BJP sources in Bhopal claimed that one of their party workers, Hanumant Singh, was injured when a rival Congress nominee's supporter opened fire at Nainipura in Bhind. They also alleged that firing took place at Aghra under Guna Lok Sabha seat.

However, police did not confirm the firing incidents but claimed to have foiled a bid by some persons to capture a booth at Aghra in Pohri tehsil.

At least four persons were arrested at Depalpur in Indore when Congress and BJP activists clashed leaving nearly half a dozen injured.

Reports of damage to or tampering with EVMs were received from Guna, Gwalior and Bhind constituencies.

Villagers at a few places in Shajapur, Morena and Vidisha boycotted polling to protest against lack of basic amenities.

The first phase of polling for 12 Lok Sabha seats in the state on May 5 had witnessed a voter turnout of 47.34%.