Five low-caste villagers have died trying to revive an unused well in a parched region of northern India, police said Tuesday, as the country reels under one of the worst droughts on record.

The five men, from India's lowest Dalit caste, were killed by toxic gas in the pit of the well in Haryana state's Jind district on Monday when they went in to clean it.

"The well had not been in use for about five to six years and a poisonous gas had formed in its depths. The five men inhaled that and died," local deputy police chief Virender Singh told AFP.

Reports said villagers had complained local authorities were doing nothing to alleviate an acute shortage of drinking water in the area, forcing the men to go down the well.

India is in the grips of its worst water crisis in years, with the government saying about 330 million people, a quarter of the population, are suffering from drought after two weak monsoons.

Poor rains have prompted extreme measures, including restricting water, stationing armed guards at reservoirs and sending water trains to the worst-affected regions.

Last week India's Supreme Court strongly criticised Haryana and two other states over their handling of the crisis, saying they had failed even to acknowledge the problem.

Singh denied there was a shortage of drinking water in Jind and said the villagers had not formally complained, or asked for the well to be revived.

"They did it hoping to restore water in the well for bathing purposes or washing utensils, for daily things, not for drinking," he said.

India's Prime Minister Narendra Modi has been meeting with the chief ministers of affected states as the national government comes under intense pressure to ease the crisis.