Police have posted photos of more than 20 suspects on social media websites to solicit clues, as investigations continue into the beatings and looting during anti-Japan protests last week.

So far, 18 people in Guangdong province, six in Shandong province and five in Hunan province, have been detained on suspicion of causing injury, vandalizing Japanese-brand cars and Japan-related businesses, and looting as demonstrations flared in more than 80 Chinese cities.

The protests erupted after Japan "nationalized" the Diaoyu Islands on Sept 11. Those islands have belonged to China for centuries.