Hundreds of students in South Korea have burned Japanese flags in protest over Japanese Prime Minister Junichiro Koizumi's visit to a Tokyo war memorial shrine.
Students threw punches and kicks at riot police who blocked them from marching to the Japanese Embassy in central Seoul.
Police fought back with plastic shields and kicks.
"Let's execute Koizumi and Japanese militarism" the students chanted as they burned paper flags.
In a separate rally in a nearby park, 50 elderly Koreans burned a Japanese flag and a large picture of Mr Koizumi with his mouth dripping with blood.
They waved pickets urging people not to buy Japanese goods.
A man covered his van with anti-Japanese slogans and drove through downtown Seoul with an effigy of Japan's wartime emperor chained to the vehicle.
Hours later, Deputy Foreign Minister Choi Sung-hong called in Japanese Ambassador Terusuke Terada to express South Korea's "deep concern" that Mr Koizumi ignored neighbours' appeals not to visit the shrine.
"We have repeatedly said that the Japanese prime minister should not pay tribute to those war criminals who destroyed world peace and inflicted indescribable harm on the neighbouring countries."