As the ruling Chinese Communist Party gears up for a massive military parade to mark the end of World War II in September, authorities across the country are detaining former army veterans, tightening controls on ethnic minority groups, and rounding up anyone with a complaint against the government.

Thirty heads of state, including Russian president Vladimir Putin and South Korean president Park Geun-hye, will attend China's celebration on Sept. 3 of its victory over Japan, although Japanese prime minister Shinzo Abe won't be among them, the foreign ministry said.

Guests also include former British Prime Minister Tony Blair, Myanmar president Thein Sein, Vietnamese president Truong Tan Sang, and senior North Korean official Choe Ryong-hae.

Beijing is already under tight security as crack People's Liberation Army (PLA) troops practice with military hardware by night along the city's tree-lined boulevards, residents said.

A Beijing resident surnamed Li said she had been refused entry to Tiananmen Square at the weekend, amid tight security.

"I tried to go to Tiananmen [on Sunday], to go onto the Square, but I couldn't get in," Li said. "They're not allowing people to go in there right now, although you can go past it in the bus."

Petitioners targeted

Nationwide, police are targeting anyone with a potential grievance against the government, including petitioners, former PLA soldiers protesting a lack of pension, and ethnic minority groups.

more China on High Alert, Detains Critics, Protesters Ahead of War Parade