For nearly seven weeks, Japanese troops raped and killed the civilian population and looted and burned the city, historian Jonathan Spence wrote in The Search for Modern China. Beijing puts the number of victims at 300,000.

Shanghai's Oriental Morning Post reported that the remains of a further 19 victims had been unearthed on the site of the memorial last year.

'This is the best counter-attack to those Japanese rightist forces who deny history. Faced with these remains, no one is capable of denying the opinion of history,' it quoted the head of the memorial, Zhu Chengshan, as saying.

The renovation of the memorial, specifically for the 70th anniversary, started in December 2005. Officials say the project will increase the total area of structures on the site by about nine times.

A Japanese diplomatic source said he had no knowledge of organised protests planned for the day. In 2005, tens of thousands of people staged anti-Japanese protests in Shanghai and other mainland cities with the tacit approval of the government.

Ties improved after Shinzo Abe took office as prime minister of Japan last September, replacing Junichiro Koizumi, who had angered China and other Asian countries with his visits to the Yasukuni Shrine, which honours Japan's war dead, including 14 class A war criminals from the second world war. Mr Abe's successor, Yasuo Fukuda, has worked to maintain good relations with Beijing.

'To cherish the improvements made in Sino-Japanese relations, to achieve long-term friendship between the two countries, we should keep this part of history firmly in mind,' Foreign Ministry spokesman Qin Gang said in Beijing yesterday.

One analyst said a continuation of the healthy relationship hinged on several factors. 'The political relationship of the two sides has improved. It's not because of China's huge development, but due to the changing perceptions of the Japanese mainstream,' said Liu Jiangyong, a professor at Tsinghua University's Institute of International Studies.

'But how long the current relationship will last depends on the cabinet's policy and whether its [hold on] power is stable.'

Feelings among Chinese over Japan's wartime atrocities still run deep despite the passage of time. 'Although some Japanese people are kind and friendly, the government still avoids confessing past mistakes such as the 'comfort women'. So I think the country will never change its attitude,' unemployed Zhang Yuxing said, referring to women forced into sexual slavery.

But some younger people have a different impression.

'Neither the media nor the people should focus too much on past disputes, which won't contribute to bilateral co-operation,' said Zhou Xiang, who works for an internet company.

Additional reporting by Lilian Zhang and Kristine Kwok