Police in India have arrested a computer researcher for refusing to reveal how he got hold of an electronic voting machine (EVM) and exposed holes in the country's election system.

Hari Prasad was arrested in Hyderabad and is now being held in Mumbai. It is reported that he has been charged with stealing one of the machines used in elections earlier this year.

Last year, officials from the Election Commission of India challenged Prasad, who had raised concerns about the safety of electronic voting, to prove their machines were flawed. But they then refused to give him access to one of the devices.

Somehow Prasad and his team of researchers got hold of one. After the election they released a video showing how they had attacked the machine and changed results.

One of the attacks involved replacing the display board of the machine with a similar component that could be controlled by a Bluetooth connection and steal a percentage of the votes for one candidate.

Another attack found a way of changing the number of votes recorded by the machine in the period between the closing of the polls and the counting of the votes, which in India can take several weeks.

Electronic voting is a controversial topic in India and earlier this month more than two dozen scientists and researchers wrote to India's chief election commissioner voicing their concerns about electronic voting machines. They want some form of paper trail to accompany each vote.

Some political parties opposed to the electronic devices have arranged for more candidates than can be listed on an EVM to stand in elections, forcing the use of old-fashioned ballot boxes.