China's aluminium imports in December rose 40.5% from the previous month, customs data showed on Monday, snapping three months of declines and extending 2020's position as a record year.

The world's biggest aluminium producer, usually has little need for overseas supply but a rapid demand recovery after the coronavirus outbreak saw Shanghai prices surge above London, opening up an arbitrage for cheaper imports.

The arb closed in the final quarter, but December arrivals of unwrought aluminium and aluminium products were still the highest since September at 265,569 tonnes, the General Administration of Customs data showed.

That was up from 188,973 tonnes in November and up 147.3 year-on-year.Full-year shipments in 2020 were 2.7 million tonnes, up 318.7% on 2019.

Imports - which include both primary aluminium and unwrought alloy - surpassed the previous annual record, set in 2009, in just 11 months of 2020, with China turning net importer in July and August for the first time in over a decade.

China's aluminium exports in 2020 fell to 4.86 million tonnes, customs said on Jan. 14. That was the lowest annual total since 2017.

Primary aluminium production in China meanwhile rose to a record 37.08 million tonnes last year, data from the National Bureau of Statistics showed earlier on Monday.