A spokesman with the Hong Kong and Macao Affairs Office of the State Council Wednesday called for "punishment according to law" of the person who physically attacked Hong Kong Chief Executive Donald Tsang Tuesday.

"We express our grave concern over the incident," said the spokesman.

Tsang was assaulted by protesters Tuesday while visiting an exhibition at the Hong Kong Museum of History.

According to reports, one of the protesters, who were allegedly organized by the League of Social Democrats, hit Tsang in the chest. Hospital sources later said Tsang had received a superficial injury.

The spokesman said Tsang was locally elected chief executive of the Hong Kong Special Administrative Region (SAR) government in line with the region's Basic Law and related laws, and was appointed by the central government.

"The chief executive should be respected and his personal safety should be effectively protected," said the spokesman. "We believe (perpetrators of) such violent activities should be punished according to law."

The exhibition was held to mark the centenary of the 1911 Revolution that ended imperial rule in China.