China-Japan row: objects thrown at US ambassador's car
20 September 2012 Last updated at 09:40 BST
The US ambassador's car was surrounded at the gates of the American embassy in Beijing.
The demonstrators chanted anti-American slogans, and threw small objects at the vehicle.
Tensions were high on Tuesday after days of sometimes violent anti-Japanese protests in China, over a chain of disputed islands in the east China Sea.
Martin Patience reports.