China's aluminium production fell 1.6% from a year earlier in September, official data showed on Friday, as ongoing outages at two key smelters leave the world's top aluminium producer struggling to register annual output growth.

China churned out 2.90 million tonnes of the metal last month, the National Bureau of Statistics said, down 2.5% from 2.973 million tonnes in August.

Top producer China Hongqiao Group's facilities were hit by flooding on Aug. 11, and Xinfa Group also closed pot lines due to an explosion a week later, meaning September was the first full month with those lines shutdown. Smelting lines usually take several months to fully resume production.

The daily average output still managed to climb to 96,700 tonnes per day in September, according to Reuters calculations, up from about 95,900 tonnes per day in August, which has one more day. The September daily rate was the highest since June.

The Xinfa and Hongqiao incidents took about 1,300 tonnes a day from the market, said Paul Adkins, managing director of consultancy AZ China. Adkins said this had, however been offset partly by the restart of China Zhongwang Holdings' smelter in the north astern province of Liaoning and a capacity addition by Xinfa in Guangxi in China's south.

In the first nine months of 2019, China produced 26.37 million tonnes of aluminium, up 1.1% from a year earlier.

Shanghai aluminium prices fell by 1.8% in September amid lacklustre demand in China, and are currently hovering just below the 14,000 yuan ($1,980) a tonne mark often considered a break-even price for Chinese smelters.

The current aluminium price "is just high enough above cost of production" to allow smelters to launch or resume operations after shutdowns, AZ China's Adkins said.

Meanwhile, China's September production of 10 nonferrous metals - including copper, aluminium, lead, zinc and nickel - came in at 4.97 million tonnes.

That was up 1.2% from 4.91 million tonnes in August and 5.1% year-on-year, the bureau said. The monthly total was the second-highest on record. On a daily basis, it set a new all-time high of about 165,700 tonnes a day.