A leading Syrian opposition figure says supporters of President Bashar Assad pelted the U.S. ambassador with tomatoes as he entered an office for a meeting and then tried to storm the office, the Associated Press reported.

Hassan Abdul-Azim, who heads the outlawed Arab Socialist Democratic Union party, said ambassador Robert Ford was meeting with him in Damascus when the Assad supporters tried to force their way in, breaking some door locks. Office staff prevented them from rushing in.

He said Ford was still inside his office with about 100 pro-government protesters outside. He said Syrian security arrived about an hour after the attack began.

Ford has been an outspoken critic of Assad's crackdown on an uprising against his rule.