Protests broke out in at least six Chinese cities on Sunday as people took to the streets after Japanese nationalists landed on an island claimed by both countries, state media said.
The nationalists raised Japanese flags on Uotsurijima just days after Tokyo deported pro-Beijing protesters who had landed on the island. China had warned against acts "harming" its territorial sovereignty.
More than a hundred people gathered near the complex housing the Japanese consulate in China's southern city of Guangzhou, chanting "Japan get out of the Diaoyu Islands," the official Xinhua news agency said.
In nearby Shenzhen, which borders Hong Kong, protesters gathered at an outdoor plaza, waving Chinese flags and shouting slogans, Xinhua said, but did not give the number of participants.
Zhang Pei, one participant, said protesters were marching towards the train station on the border with Hong Kong.
"The demonstration is strung out for seven to eight kilometres (four to five miles). Many police are escorting us along the street," he told AFP by telephone.
He could not give an estimate of the number of protesters, but said participants were swelling as the march continued.
Xinhua said protests also took place in four other cities, including eastern Hangzhou and Qingdao, as well as the northeastern cities of Shenyang and Harbin.
Beijing on Saturday rebuked Japan over the planned island visit.
"China has made solemn representations to Japan, demanding that it immediately cease actions harming China's territorial sovereignty," the foreign ministry said in a statement.
Anti-Japan protests have broken out in several cities in the past week, including the capital Beijing, commercial hub of Shanghai and Qingdao and Binzhou in the eastern province of Shandong, state media and witnesses said.
The island is part of a chain claimed by China. China calls the archipelago Diaoyu, but it is controlled by Japan, which calls it Senkaku.
On Saturday, hundreds gathered in the northern city of Xian to protest over the detention of 14 pro-China activists and journalists who had sailed from Hong Kong to land on the islands, Xinhua said in a separate report.
Japan on Friday deported the 14 people, who were arrested after arriving in the area on Wednesday.