A video game backed by China's military that lets players fight enemy forces in islands disputed between Beijing and Tokyo was set for release Thursday.
"Glorious Mission Online", China's answer to "Call of Duty", marks the 86th anniversary of the founding of the People's Liberation Army (PLA).
An online version of an earlier first-person shooter used by the PLA to train troops, the game features the East China Sea islands known as Diaoyu by Beijing, which claims them, but controlled by Tokyo, which calls them Senkaku.
Tensions have been mounting over the dispute, and a press release for the game says: "Players... will fight alongside Chinese armed forces and use weapons to tell the Japanese that 'Japan must return our stolen territory!'"
Images from the game's website are labelled "Guard the Diaoyu islands", and a trailer posted online features shots of Japan's new hardline Prime Minister Shinzo Abe.
It also shows planes taking off from a computer generated version of China's first aircraft carrier, the Liaoning, which went into service last year.
The game was only due to become available at 5:00pm (0900 GMT), but its designers Giant Interactive Group, who developed it jointly with the PLA, told AFP millions of users had already registered to play.
Giant co-operated closely with the PLA while working on the game to ensure that the appearance of guns and the voices of in-game soldiers were accurate, said company vice-president Gu Wen.
"Our relationship with the military is like the relationship between the US army and Hollywood," he said.
"In Western games the People's Liberation Army is always the enemy, this is the first game where it is on the good side."
It will also boost recruitment for the military, he added.
"On one hand it's a training tool, on the other hand it's about army recruitment," Gu said. "The army aims at recruiting university graduates, and gaming is the most popular culture among students."