A security officer stands guard as passengers line up and wait for a security check during morning rush hour at Tiantongyuan North Station in Beijing on May 27. Beijing tightened security checks at subway stations last Saturday, following an attack in China's troubled Xinjiang region which killed 31 people on May 22, the deadliest act of violence in the region in years.
Beijing Subways Introduce 'Anti-Terror' Checks
Beijing has tightened security checks at subway stations since last Saturday's attack which killed 31 people.