Syrian demonstrators threw U.S. ambassador Robert Ford with stones and tomatoes as they were visiting an opposition figure in Damascus

Syrian demonstrators threw U.S. ambassador Robert Ford and other U.S. diplomats on Thursday with stones and tomatoes as they were visiting an opposition figure in Damascus , a witness and diplomatic sources were quoted by Reuters.

"Two embassy cars were damaged. The U.S. delegation is still there and the crowd is surrounding the building," said the witness. "They are chanting 'Abu Hafez (father of Hafez)'," the witness said, a nickname for Syrian President Bashar Assad.

The diplomats were visiting Hassan Abdul-Azim, who heads the outlawed Arab Socialist Democratic Union party. He has been demanding an end to a crackdown on opposition protesters as a condition for any talks with Assad.

Abdul-Azim told the Associated Press that Ford was still inside his office with about 100 pro-government protesters outside. He said Syrian security arrived about an hour after the movement began.

In Washington, State Department officials were not immediately available to comment.

It was the second attack on U.S. diplomats since the protests erupted in Syria in March. In July, following a visit by Ford to the city of Hama, Syrian protesters attacked the U.S. embassy compound in Damascus.