Hollywood blockbuster "Transformers" has raked in more than 100 million yuan (about US$13 million) since opening on the Chinese mainland last Wednesday, easily outperforming the first-week sales of the American films already released this year.

"Transformers spent the shortest time amassing more than 100 million yuan, compared with other American blockbusters released this year in China," said Gao Jun, spokesman of Beijing's New Film Association.

Pirates of the Caribbean 3 took nearly 80 million yuan (US$10.4 million) in its first week since its release on June 12, 10 million yuan more than "Spiderman 3" recorded in its first week.

The sci-fi action movie about warring robots, adapted from the popular animated TV series in the 1980s, has mainly attracted China's "80s" generation as its target audience.

"It is not surprising that Transformers has done so well at the box office, as the 80s generation has turned out in force and the movie was released during the summer vacation," Gao said.

The quality of the movie itself contributed to its box office success too. "It was a good sci-fi movie with not only hi-tech and skillful animation, but more importantly flawless story plots," said Gao.

Meanwhile, the US documentary "Nanking" chronicling Japan's notorious 1937 invasion of the Chinese city Nanjing, and which opened in China on July 7, was left trailing in the dust.

The 90-minute documentary "Nanking" features interviews with Chinese survivors and Japanese soldiers, along with pictures, letters and diaries read by actors portraying Westerners who helped save more than 200,000 Chinese refugees in Nanjing.

"Transformers dominates the cinema screens, so it is natural to dominate the box office," said one person named "movie worm" on an Internet film forum.

"Profit-driven cinema managers always abandon serious movies like 'Nanking' to make way for blockbusters like 'Transformers'. It surely has a bad impact on the diversity of the movie market," the netizen said.

The Shanghai New Century Cinema screened "Transformers" 30 times on July 15 but "Nanking" was only screened once on the same day at the same cinema.