A news report Thursday says aides to disgraced Chinese politician Bo Xilai were discovered last year to have been tapping phone calls to top national leaders including President Hu Jintao.

The New York Times says sophisticated devices identified the tap on a call between Mr. Hu and a senior anti-corruption official who was visiting Chongqing, the massive city in western China then ruled by Bo.

Bo was fired as the city's Communist Party chief and subsequently stripped of all party posts in a scandal that has captivated Chinese citizens. His downfall has been mainly attributed to charges that Bo's wife was implicated in the murder of a British businessman, but the Times quotes officials as saying the wiretapping was also a factor.

The newspaper says almost a dozen people with close ties to the ruling party have confirmed the wiretapping, part of a widespread bugging program put in place across Chongqing several years ago.

The sources, none of whom is identified by name, say the bugging was part of an anti-crime crackdown implemented by Bo's former police chief, Wang Lijun. One source is quoted describing Wang as “a bugging freak.”

Wang eventually broke with Bo over the murder of British businessman Neil Heywood. The scandal came into public view when Wang appeared at the U.S. Consulate in nearby Chengdu, reportedly to seek asylum. Authorities moved Wang to Beijing, and he has not been heard from since.

The Times says the wiretapping program was well known to targets of the anti-crime crackdown in Chongqing, which is said to have included many legitimate businessmen. Sources tell the newspaper they were amazed by the “scale and determination” with which police intercepted their communications.

The paper quotes party insiders as saying the wiretapping scheme was seen as a direct challenge to the central authorities in Beijing.