Police across China battled to control widespread anti-Japan demonstrations for a second day on Sunday, as Beijing appeared to be treading a fine line between sending a political message to Japan without allowing social unrest that could destabilise the political transition in China.

Thousands of apparently well-organised demonstrators, some of them carrying portraits of former Communist party leader Mao Zedong, were met with a heavy police presence in several cities nationwide as the Japanese prime minister called on Beijing to protect the country's nationals and companies in China.