Vietnam President Lam takes on duties of party chief as Trong focuses on health

The extraordinary move comes after months of speculation that Trong's health was weakening. The party did not clarify what treatment he is receiving.

Lam, a former head of internal security, has been widely seen as a top candidate to replace Trong when his term ends in 2026. The party's powerful Politburo has tasked him with presiding over "the work of the Party Central Committee, the Politburo and the Secretariat," according to a statement from the party's central office.

Though Vietnam officially has no paramount ruler, the party chief holds the most powerful position in the Communist-ruled nation. Trong, 80, has been in the post since 2011.

Trong, a Marxist-Leninist ideologue, has since 2017 unleashed what many see as a China-style crackdown on corruption known as "blazing furnace". But in recent months, he has appeared fragile in public events and missed several top-level meetings.

In a surprise move, the Politburo awarded Trong on Thursday with the Gold Star medal, the country's highest honour for public officials.

Lam was elected president in May after several top leaders quit amid accusations of unspecified wrongdoing, part of the sweeping anti-graft campaign launched by Trong.

Lam, a key player in the crackdown, promised after his election to "resolutely and persistently continue the fight against corruption".

Vietnam's main stock market edged up 0.5% after the announcement.

A Hanoi-based senior Western diplomat said he saw Lam's expanded powers as "Good for stability."

But the diplomat, who declined to be identified, added: "We'll need to see if this has an impact on economic, foreign and domestic policies and in which direction."