Chirac spoke as his government minister for the elderly, Hubert Falco, speaking after a Cabinet meeting, told reporters that "most probably" some 10,000 people had died from the heat, though there was no specific figure yet available. The previous official estimate was 5,000.
Falco was the first government official to confirm estimates released a day earlier by France's largest chain of undertakers that the death toll from the heat when temperatures topped 104 degrees Fahrenheit, could reach 10,000.
Chirac, under fire from opposition politicians and newspapers for not speaking earlier, Chirac did not give a death toll figure, but said the heat wave "caused a very large number victims."
Chirac said he has asked for an in-depth study of the health system crisis and its causes from his embattled government.
"Everything will be done to correct the insufficiencies that we noted in our health system," the president said in a live address after a Cabinet meeting on the heat that baked France in the first two weeks of August.
In an apparent effort to calm the storm of criticism faced by his government, Chirac added: "Today, the time is for contemplation, solidarity and action."
It is rare for Chirac to speak directly to the nation after a Cabinet meeting. As president, he tends to stay above the fray of day-to-day domestic politics. That he chose to speak was a measure of the gravity of the crisis faced by his administration, which has been widely accused of doing too little, too late in the face of the heat wave and the scores of deaths it caused.
Chirac was speaking after three weeks vacationing abroad in Canada. He did not speak about the heat wave in public while on holiday, although his office said he was following the situation closely. Critics noted that former Prime Minister Lionel Jospin broke off a vacation to Egypt when France suffered storms in 1999.
Funeral home chain OGF, which holds about a quarter of the market, said it had counted 2,600 more deaths in the first three weeks of August than in same period of last year. It estimated that figure meant that more than 10,000 people died nationwide.
On Monday, Health Minister Jean-Francois Mattei said it was "plausible" that as many as 5,000 people had died during the heat wave — the largest such government estimate until Thursday.
Health workers said one of the reasons why the death toll was so high was that families abandoned their elderly relatives alone at home while they went away for August vacations.
Chirac said the crisis had shed light "on the solitude of many of our aged or handicapped citizens" and promised to propose measures this autumn to better care for them, although he did not say what the measures would be.
Chirac promised a review of France's health surveillance, alert and prevention bodies "to avoid such dramas in the future."
He also said emergency services would be given the means to better deal with temporary crises, although he stopped short of saying whether the government, already criticized by the European Union for overspending on public services, would give emergency services more funding.
Chirac called the heat wave "exceptional." The heat wave was the longest and hottest to ever hit France, with temperatures that topped 104. He noted that "many fragile people died alone in their homes."
Doctors say heat stroke and dehydration were often the cause of death.
According to the U.S. Centers For Disease Control and Prevention, over the past 20 years heat killed more Americans than hurricanes, lightning, tornadoes, floods, and earthquakes combined.
Within a five-day period, the 1995 Chicago heat wave killed between 525 and 726 people, depending on the method used for determining which deaths were attributable to the high temperatures. In the heat wave of 1980, some 1,250 Americans died. A heat wave earlier this year in India killed at least 1,200 people.