Police have detained at least 11 people accused of vandalizing cars and shops in Guangzhou during weekend nationwide protests against Japan's "nationalization" of China's Diaoyu Islands.

The government on Monday called for people to demonstrate in an "orderly and rational" manner, one day ahead of the 81st anniversary of the Sept 18 Incident, which marked the start of Japanese occupation of Northeast China in 1931.

More than 80 Chinese cities have seen residents take to the streets to protest Japan's "purchase" of the islands, according to media.