The first vote in the seven-phase election will be cast on Friday, with results set for June 4, as Prime Minister Narendra Modi looks set to win a historic third term in the face of a straggling opposition challenge.

The Election Commission has to set up more than one million polling stations for the nearly two-month duration, with 15 million officials and security personnel fanning out for the task.

"Whether the polling officers have to climb down mountains, go through rivers or fly by choppers, the Election Commission is doing its job to ensure that nobody misses out on their voting rights," said W Moning Belgit, one of its officials.

He was speaking after having led a small crew that trekked for hours on Thursday to reach 139 voters in a remote, hilly village in the eastern state of Meghalaya.

His team went up 12km of mountains, climbed down hundreds of steps and crossed a river to reach the village of Nongriat, where they will set up a polling booth under the thatched roof of a school.

In Friday's first phase of voting in 21 states and territories, as many as 102 constituencies will exercise the franchise, from a total of 543 in the lower house of parliament.

The effort is the "world's largest election mobilisation exercise of man and material", the Election Commission said in a social media post on Wednesday.

Scores of polling officers have been flown to remote areas in the rugged Himalayas and the central Indian constituency of Gadchiroli-Chimur, beset by Maoist violence, to which 850 polling staff are being sent, the poll body said.

Besides the insurgents, officers must keep a lookout for a wild elephant roaming the Gadchiroli area after killing two farmers, although trackers are trying to keep it from further mayhem, the Indian Express newspaper said.

Australian Associated Press