With July spot aluminium prices averaging 13,796 yuan, smelters were making a loss of 92 yuan a tonne on paper, "significantly narrowed" from June, the research house says in a note based on a survey of 75 smelters.

Spot prices for alumina, a substance used to make aluminium, in northern China slipped to 2,440 yuan a tonne on Monday, the lowest since May 2017, on oversupply.

China's annual operating aluminium smelting capacity stood at 36.52 million tonnes last month, down 2pc year-on-year but up 0.1pc from July, Antaike says in a separate note.

Smelter operating rates were at 90.3pc, it says, noting that 90,000 tonnes of capacity was put into production in July and another 170,000 tonnes restarted, while 220,000 tonnes was cut.

China's National Bureau of Statistics is due to report an aluminium production number for July on Aug. 14.