Another high-ranking official has been nabbed in China's anti-graft campaign, but this time it involves an ally of President Xi Jinping.

The official Xinhua news agency last night reported that Tianjin's mayor and acting party boss Huang Xingguo has been placed under investigations for "serious disciplinary violations", a euphemism for corruption.

His downfall is seen as a possible sign of weakness in Mr Xi's power base and also a sign that the jockeying for power in the lead-up to next year's leadership transition at the 19th Party Congress is intensifying.

Mr Huang, 61, had worked briefly with Mr Xi when the latter was provincial party chief of Zhejiang from 2002 to 2007.

The Zhejiang native, who had worked his way up in the province since 1972, was then party boss of Ningbo city and a member of the provincial party committee headed by Mr Xi.

In November 2003, he was appointed deputy party boss and vice-mayor of Tianjin, where he rose through the ranks to become the municipality's mayor by 2014.

After Mr Xi took power in late 2012, Mr Huang was among a small group of the Chinese leader's former subordinates touted to be taking up bigger posts.

But murmurings began when Mr Huang was not promoted to Tianjin party boss after Ms Sun Chunlan left the post in late 2014 to head the United Front Work Department. Instead, he was made acting party boss.

Doubts over Mr Huang's political career deepened after chemical explosions at a Tianjin warehouse in August last year killed at least 165 people and injured 798 others.

But there were some who believed that Mr Huang, a member of the Communist Party's Central Committee, might still be formally appointed Tianjin party chief and move up at next year's congress.

The post of party secretary of one of China's four municipalities - the others being Beijing, Shanghai and Chongqing - usually leads to a seat in the elite Politburo.

Mr Huang's last public appearance took place last Friday when he hosted a delegation from Taiwan's Kuomintang in Tianjin.