Sarkozy said the incident showed "the importance of freedom of information".
"This shows that enough is enough, this regime must go. There is no reason why Syrians should not have the right to live their lives, to freely choose their destiny," Sarkozy said.
France identified the two Western reporters killed in Syria on Wednesday as veteran American war correspondent Marie Colvin of Britain's Sunday Times and freelance French photojournalist Remi Ochlik.
Activists said they were killed and three others wounded when forces loyal to Assad's regime shelled a makeshift media centre in the Baba Amr district of Homs.
The French daily Le Figaro said one of its reporters, Edith Bouvier, had been among three journalists wounded in the same incident.
France on Wednesday demanded access to the victims of the attack and summoned Syria's envoy to Paris.
"Following the information we have from Homs that a group of journalists were victims of shelling, I am asking the Syrian government to immediately stop attacks and respect its humanitarian obligations," Foreign Minister Alain Juppé said in a statement.
"I have asked our embassy in Damascus to require the Syrian authorities provide secure medical access to assist the victims with the support of the International Committee of the Red Cross," Juppé said.
He said he had also "summoned the Syrian ambassador to Paris to express these requirements and to remind him of the intolerable nature of the Syrian government's behaviour."