The rate of deaths in the Paris region during a record-breaking heatwave last month was more than double normal levels, France's health agency said on Friday.

"A very high excess mortality rate was observed in Ile-de-France (between June 22 and 28) during the heatwave," Sante Publique France said in a report recording 3,000 fatalities -- "1,565 more deaths than expected".

The Paris region was one of the hardest hit in terms of excess deaths during the June heatwave, one of three that swept across France since May.

Scientists have linked the increasing frequency of extreme weather to man-made climate change.

Initial excess death figures from the June heatwave showed 2,000 more fatalities than expected across France, but the number was expected to rise.

The figure from the Paris region "mainly concerned people over 65, who accounted for 82.4% of the deaths", the agency said, adding that the number could still increase.

Deaths linked to heatwaves are not limited to the immediate effects of high temperatures, such as dehydration and hyperthermia, as some effects take days to manifest.

France's weather service said the 14-day June heatwave was even "more intense" than the 2003 episode that claimed 15,000 lives in France -- although it was two days shorter.

The heatwave swept across Europe, breaking all-time temperature records in several countries.

World Weather Attribution, a network of climate scientists, said last month that the heatwave was the "most severe ever recorded" based on a three-day forecast of average peak temperatures over the region studied.

Such a heatwave would have been "virtually impossible" without the influence of climate change, they said.