They were among the 10,000 people said to have attended an official ceremony in Tiananmen Square on Saturday.
After a 60-gun salute and the release of 6,000 doves, top Communist leaders and officials laid wreaths at the Monument to the People’s Heroes.
Many millions of Chinese citizens died during Japan’s 1931-45 occupation.
Relations between the two countries have reached a low point ahead of the anniversary commemorations.
Earlier this year, there were violent anti-Japanese protests across China after Tokyo approved a set of controversial history textbooks, which critics said whitewashed its wartime record.