The bomb went off at around sunset in a crowded outdoor cafe in a plaza outside the city's historic Hussein mosque, one of the largest and holiest in the city.
Officials say 19 other French teenagers were among the wounded, as were three Saudis and an Egyptian. Three of the teenagers were in serious condition Monday, reports the Associated Press. Confusion over the death toll immediately followed the attack, as the Monitor reported here on Sunday.
The bomb was the first in Cairo since April 2005. No group has yet claim responsibility for the attack, although on Sunday police arrested three suspects.
"Three people there were arrested on the site as suspects after the attack," a police official told Agence-France Presse. "Around 15 others are being questioned as witnesses."
Shaken by the bombing, finger-pointing across the Egyptian capital has already begun.
Egypt has kept its land border at Rafah more or less closed since Hamas took power of Gaza in June 2007. For more on the tension between Egypt, Israel, and Hamas on the smuggling across the border, click here or here.
"Definitely, this bombing has to do with the war on Gaza and the animosity aroused against Egypt in the region," he said.
Diaa Rashwan, an expert on Islamist movements at the Ahram Center, a Cairo think tank, said that if people with radical views are inclined to attack soft targets, then local context or current events may be relatively unimportant.
"If we want to think the way militant Islamists think, then time does not matter because it is open-ended," he says. "They see the world divided between the camp of Muslims and the camp of nonbelievers, so timing does not matter and neither do events in Gaza or Iraq."
"It is not a problem of time, it is a problem of possibility," he adds. "What they did yesterday was possible, so they did it."
Some in the country's opposition movement see a possible government plot in the timing of Sunday's attack.
In less than a week, parliament is set to vote on an antiterrorism law that would effectively make the country's 28-year state of emergency permanent.
"Nothing better to justify the passing of such a publicly despised law than to have a nice explosion a few days before its passing," writes the libertarian blogger Sandmonkey on his blog.