The United States says Syrian President Bashar al-Assad has “lost legitimacy,” while France has renewed its call for the United Nations Security Council to take action in the on-going crisis.

In Washington's strongest condemnation of Mr. Assad since his security forces launched a violent crackdown on pro-democracy protesters in March, Secretary of State Hillary Clinton said the authoritarian leader “is not indispensable,” and that the U.S. has “nothing invested in him remaining in power.”

French Prime Minister Francois Fillon said Tuesday it becomes more difficult for Mr. Assad to remain in power with each passing day. He also told Europe-1 radio that the U.N. Security Council's “silence” on Syria has become untenable, and that Russia and China are blocking a U.N. resolution.

Clinton condemned recent mob attacks on the U.S. embassy and the American ambassador's residence in Damascus, as well as separate assaults against French diplomatic missions in the country.

She accused Mr. Assad's government of attempting to divert attention from its brutal domestic crackdown, and she demanded that Syria uphold international treaty obligations to protect foreign diplomats and missions. She also charged that Damascus has accepted aid from Iran to repress the Syrian people.

Crowds of Syrians loyal to Mr. Assad surged into the U.S. embassy compound in Damascus Monday. Attackers broke windows, raised a Syrian flag on the grounds and wrote anti-U.S. graffiti on walls. The mob left after the brief incursion was pushed back by U.S. Marine guards.

The French embassy gates were also the scene of protests on Monday. French security guards fired in the air to keep demonstrators from entering the grounds. Officials said three embassy staffers were injured.

The protests come amid rising tensions with Syria's government after last week's visit by the U.S. and French ambassadors to the flashpoint city of Hama.

Ambassador Robert Ford and French Ambassador Eric Chevallier traveled to Hama Thursday and Friday to show solidarity with its residents, who have come under attack from government forces while staging some of the largest protests to date against Mr. Assad.

Syria's foreign ministry called the visits “flagrant interference” in the country's internal affairs aimed at undermining its stability.

Rights groups say Syrian security forces have killed at least 1,600 civilians during the crackdown, while the government blames the violence on terrorists and Islamists who it says have killed hundreds of security personnel.