A diplomat in Saudi Arabia said on Wednesday that 68 Indian nationals died during the hajj pilgrimage this year marked by searing heat, bringing the overall tally to more than 600.

"We have confirmed around 68 dead... Some are because of natural causes and we had many old-age pilgrims. And some are due to the weather conditions, that's what we assume," the diplomat, who spoke on condition of anonymity, said.

The new toll comes after two Arab diplomats said on Tuesday that 550 deaths had been recorded during the hajj, one of the five pillars of Islam that all Muslims with the means must perform at least once.

That figure included 323 Egyptians and 60 Jordanians, the Arab diplomats said, and one specified that nearly all the Egyptians died "because of heat".

Fatalities have also been confirmed by Indonesia, Iran, Senegal, Tunisia and Iraq's autonomous Kurdistan region, though in many cases authorities have not specified the cause.

The total reported dead so far is 645, according to a tally.

Last year more than 200 pilgrims were reported dead, most of them from Indonesia.

Saudi Arabia has not provided information on fatalities, though it reported more than 2,700 cases of "heat exhaustion" on Sunday alone.

The diplomat who confirmed the Indian fatalities said there were also some Indian pilgrims missing, but he declined to provide an exact number.

"This happens every year... We can't say that it is abnormally high this year," he said.

"It's somewhat similar to last year but we will know more in the coming days."

For the past several years the hajj has fallen during the sweltering Saudi summer.

According to a Saudi study published last month, temperatures in the area where rituals are performed are rising 0.4 degrees Celsius (0.72 degrees Fahrenheit) each decade.