Japan's prime minister sent a senior diplomat to Beijing on Tuesday with a letter for Chinese President Hu Jintao in an apparent attempt to ease tensions between the two Asian giants over a territorial dispute.

The trip by Parliamentary Senior Vice Foreign Minister Tsuyoshi Yamaguchi comes a day after a car carrying the Japanese ambassador in the Chinese capital was attacked by a man who ripped the Japanese flag off, damaging the vehicle's flagpole and prompting protests from Tokyo.

Japanese Foreign Minister Koichiro Gemba called the incident "deplorable" and demanded an investigation. He said a national flag "is a symbol to the nation's dignity that needs to respected."

Thousands of Chinese have gathered in anti-Japanese street protests in recent weeks amid renewed diplomatic tension over a cluster of uninhabited islands in the East China Sea controlled by Japan but also claimed by China and Taiwan.

Earlier this month, Japan detained and later released 14 activists from Hong Kong who landed on the islands, called Diaoyu in Chinese and Senkaku in Japanese, which are near key sea lanes and surrounded by rich fishing grounds and as-yet untapped underground natural resources.

Prime Minister Yoshihiko Noda's letter to the Chinese president touches on "developing Japanese-Chinese relations in a stable manner from a broad perspective," said Chief Cabinet Secretary Osamu Fujimura. He and other officials declined to be more specific.

Yamaguchi was to meet with Chinese counterparts to discuss a range of regional and global issues, including tensions on the Korean Peninsula, said Masaru Sato, a spokesman at the Foreign Ministry.

The Japanese Embassy in Beijing said in a statement that Ambassador Uichiro Niwa was returning to the embassy on Monday when his official car was stopped by two other vehicles. It said a man jumped out of one of the vehicles and pulled the flag off the front of Niwa's car. Only the flagpole was damaged, the embassy said.

China's Foreign Ministry expressed deep regret over the incident and said authorities would spare no effort to prevent a recurrence. It said the government has consistently fulfilled its international obligation to protect the safety of foreign embassies and personnel.

An editorial in the Chinese state-run Global Times newspaper Tuesday said that the man involved in the attack had not yet been identified, but that if he was Chinese, his act was "a stupid one" and not representative of the Chinese people.

Chinese authorities face the tricky balance of appearing tough on territorial claims without stirring anti-Japanese sentiment that could threaten relations with Tokyo or even backfire into criticisms of China's government.

"Chinese people should remain calm and civilized when expressing their patriotism. Any actions and protests must remain within the law," the editorial said.


Associated Press writer Gillian Wong in Beijing contributed to this report.