BEIJING — China replaced its finance minister yesterday amid news reports that he was involved in a sex scandal just weeks ahead of a major Communist Party meeting that will set the country’s policies for the next five years.

The chief of secret police and other top officials were also replaced as part of a political housecleaning that marked a departure from previous practice where top government portfolios changed hands after party congresses held once in every five years.

This year’s congress in October will see President Hu’s further put his stamp on the party’s lineup and national priorities. The reshuffling appeared aimed at making the promotion of Mr. Hu’s allies during the congress less jarring. Jin Renqing, the finance minister since 2003, was resigning “for personal reasons,” a Cabinet spokeswoman said without elaborating, fueling speculation that Mr. Jin had run afoul of the party leadership.

Rumors that Mr. Jin, 63, was being ousted as finance chief had circulated for days, raising concerns in global financial circles.

There was no immediate word on why he resigned. But similar cases in the past have been attributed to marital infidelity or health or family problems. Mr. Jin is still two years below the official retirement age for officials at the central government level.

“It’s a little hard to know what really drove this but I’ve certainly heard rumors that a sex scandal was involved and this is something that has brought down others,” Kenneth Lieberthal, a scholar of Chinese politics at the University of Michigan, said.

The South China Morning Post, citing unidentified sources, reported Wednesday that Mr. Jin was said to have a mistress who had also been romantically linked to another official currently under investigation for corruption.

The Hong Kong Mingpao newspaper quoted sources in Beijing as saying that Mr. Jin had introduced Chen Tonghai, the chairman of China Petroleum and Chemical Corp., or Sinopec, to a woman who became Chen’s mistress. The same woman later became the mistress of Du Shicheng, a former deputy party secretary in the eastern province of Shandong who is under investigation for corruption. It did not give the woman’s name and said it was unclear what Mr. Jin’s relationship with her was.

The reports could not immediately be confirmed.

Legislative spokesman He Shaoren told a news conference that Mr. Jin was being replaced as finance minister by Xie Xuren, who runs the tax administration. Mr. Jin’s successor is not expected to make any major changes. Such policy decisions are made behind closed doors by the Communist Party leadership.