At least 33 Indian polling staff died on the last day of voting from heatstroke in just one state, a top election official said Sunday, after scorching temperatures gripped swathes of the country.

While there have been reports of multiple deaths from the intense heatwave -- with temperatures above 45 degrees Celsius (113 degrees Fahrenheit) in many places -- the dozens of staff dying in one day marks an especially grim toll.

The India Meteorological Department (IMD) said temperatures at Jhansi in Uttar Pradesh reached 46.9 degrees Celsius (116 Fahrenheit).  

Navdeep Rinwa, chief electoral officer for the northern state of Uttar Pradesh, where voting in the seventh and final stage of elections ended Saturday, said 33 polling personnel died due to the heat.

The figure included security guards and sanitation staff.

"A monetary compensation of 1.5 million rupees ($18,000) will be provided to the families of the deceased," Rinwa told reporters.

Experts say that when a person is dehydrated, extreme heat exposure thickens their blood and causes organs to shut down.

Rinwa reported a separate incident in which a man queueing to vote in the city of Ballia lost consciousness while waiting in line.

"The voter was transported to a health facility, where he was pronounced dead upon arrival," Rinwa said.

India is no stranger to searing summer temperatures.

But years of scientific research have found climate change is causing heatwaves to become longer, more frequent and more intense.

Hindu-nationalist Prime Minister Narendra Modi looks set to win a third straight landslide election victory after voting ended on Saturday.

Exit polls showed he was well on track to triumph and Modi himself was certain he had prevailed. 

The results will be formally announced on Tuesday.