The four Chongqing officers are accused of helping Gu cover up her actions during an investigation into business associate Neil Heywood's death last November, the official Xinhua News Agency said. It named them as Guo Weiguo, a former deputy chief of Chongqing's Public Security Bureau, and others prominent in police leadership: Li Yang, Wang Pengfei and Wang Zhi.

Gu's arrest and the ouster of her husband as Chongqing party chief in March sparked the biggest political turbulence in China since the putdown of the Tiananmen Square protests in 1989. The tightly orchestrated trials this week are a step toward resolving the scandal ahead of the party's once-in-a-decade leadership transition this fall.

One of China's most powerful and charismatic politicians until he was ousted, Bo had been considered a possible for the party's all-powerful nine-member Standing Committee when seven new members are appointed at the fall congress.