As the stock with the second-biggest weighting on the index, PetroChina was back in favour among traders because of optimism that its earnings will get a boost from rising crude oil prices that are trading near a four-year high in New York.

Still, some analysts said the “national team”, a term used by Chinese investors to refer to state-supported funds created during the 2015 market crash, may be behind the stock’s rise, buying it up to prevent the benchmark gauge from sinking further.

“PetroChina is the best in terms of fundamentals among all the big caps,” said Wei Wei, a trader at Huaxi Securities in Shanghai. “It’s possible that the state is buying the stock to balance the index movement while other heavy weights are not doing much to prop up the market.”

Buying of bellwether stocks such as PetroChina and Industrial and Commercial Bank of China was a frequently used tactic of the state-linked funds to stabilise equities in the aftermath of the 2015 rout that erased US$5 trillion in market capitalisation.

The rally in PetroChina’s shares comes at a time when a rebound in China’s stocks is much needed. Investors have been turning to regional markets for trading clues after a weeklong holiday, as global stocks have been battered by a liquidity squeeze amid rising US Treasury yields.

About 91 million shares of PetroChina changed hands on Tuesday, almost double its 180-day average trading volume, according to Bloomberg data. The stock accounts for 5.1 per cent of the weighting on the Shanghai Composite.

Still, analysts are not bullish on the energy behemoth. Fourteen industry analysts covering PetroChina’s stock set a 12-month price target of 7.91 yuan, implying a 14 per cent decline from the Tuesday close of 9.22 yuan, Bloomberg data shows.

PetroChina’s Shanghai-traded shares have gained 14 per cent this year, beating an 18 per cent loss on the broader benchmark index.