China’s most senior general is under investigation on allegations that include leaking information about the country’s nuclear weapons program to the United States and accepting bribes in exchange for official promotions, including the elevation of a former defense minister, The Wall Street Journal reported Sunday.

The allegations were outlined Saturday during a closed-door briefing attended by senior military officers, shortly before China’s Ministry of National Defense announced an investigation into Gen. Zhang Youxia, according to the Journal. The ministry said Zhang is suspected of serious violations of party discipline and state law, without providing details.

People familiar with the briefing told the Journal that Zhang is accused of forming political cliques and abusing his authority within the Central Military Commission, the Communist Party’s top military body. Authorities are also scrutinizing his oversight of a powerful military procurement agency, where he is alleged to have accepted large sums of money in exchange for promotions.

The most serious allegation, according to the Journal, is that Zhang leaked core technical data related to China’s nuclear weapons program to the United States.

Some of the evidence against Zhang is said to stem from an investigation into Gu Jun, the former general manager of China National Nuclear Corp., a state-owned company overseeing civilian and military nuclear programs. Beijing announced last week that Gu is under investigation for suspected violations of party discipline and state law.

In a statement, Chinese Embassy spokesman Liu Pengyu said the investigation demonstrates the Communist Party’s “full-coverage, zero-tolerance approach to combating corruption.”

Analysts say the investigation marks one of the most sweeping purges of China’s military leadership in decades, expanding President Xi Jinping’s campaign against corruption and political disloyalty within the armed forces.

Material from The Wall Street Journal was used in this story.