BEIJING — Bo Xilai, the brash Communist Party chief of the Chongqing municipality in China’s southwest, has been removed from his post, an unmistakable sign that recent scandals in that city have put an end to his political ambitions and complicated the national leadership transition that will take place in the fall.

The news, announced Thursday morning in a brief dispatch by the official Xinhua news service, said Vice Prime Minister Zhang Dejiang would replace him as party secretary of Chongqing.

Until recently, Mr. Bo had been expected to join the all-powerful Standing Committee of the Politburo, a nine-member body that effectively runs the country. Seven of the members are to be replaced, and Mr. Bo’s demotion suggests there will be more drama in a usually secret process.

Mr. Bo’s troubles began last month when his handpicked police chief, Wang Lijun, sought refuge in the United States Consulate in Chengdu, about 210 miles from Chongqing. Mr. Wang, who had come under scrutiny in a corruption inquiry, spent the night in the consulate before being escorted to Beijing by security officials. He was also removed from his post, according to state media.