The French defense minister, Jean-Yves Le Drian, has already spoken of possible “no-fly zones” over Syrian territory, from the Turkish border to Aleppo, to protect refugees, but he has provided no further details. He said the idea originated with Secretary of State Hillary Rodham Clinton and was being studied.

Mr. Hollande also said that France continued to press the Security Council for a new, more far-reaching resolution on Syria and criticized Russia and China for using their vetoes to protect Mr. Assad. He said that their “attitude is weakening our capacity to ensure the United Nations Charter is respected.”

His comments came as some of the war’s deadliest violence remained focused on the outskirts of Damascus. In Daraya, southwest of the capital, opposition activists have accused the government of killing hundreds of people over the last week.

In recent days, residents have spoken of a brutal “cleansing” operation by the military, deploying helicopters, heavy artillery and tanks to dislodge a large contingent of rebel fighters who had made Daraya a stronghold. Mass burials were held on Sunday for victims, who included women and children.

Refugees from Daraya who reached Lebanon on Monday spoke of bodies lying on residential streets and town squares, and a city choked by the smell of death. A 17-year-old refugee who fled with her family said that many of the dead were rebel fighters, but many other victims, like her uncle, who she claimed had no ties to the rebels, were civilians seized by government troops who later turned up dead, she said.

Her uncle, a 40-year-old bus driver, was taken by soldiers last Monday as he walked neighbors to a bomb shelter, she said. The next day, his body was found with knife and bullet wounds. His family, too frightened to attend his funeral, found a picture of his corpse on the Internet. Now his niece keeps the picture on her cellphone.