For December, imports fell 4.7 percent from the previous month to 429,000 tonnes from a revised figure of 450,000 tonnes in Novemeber, the General Administration of Customs said. December was also down 4.7 percent from the same month a year ago.

Annual imports of unwrought copper – which topped the previous record of 4.94 million tonnes set in 2016 – were buoyed by China's crackdown on scrap copper in 2018, part of efforts to combat pollution.

There's certainly continuing tightening pressure on China's imports of lower quality scrap so it's not a terrible surprise that China is importing more metal
Imports of Category 7 copper scrap, such as coiled copper cable and waste motors, were down sharply from 2017 and have been banned completely in 2019, while China in August slapped a 25 percent tariff on imports of scrap material from the United States, one of its top suppliers.

This has left consumers seeking more of the metal in other forms.

"There's certainly continuing tightening pressure on China's imports of lower quality scrap so it's not a terrible surprise that China is importing more metal," said Lachlan Shaw, a commodities strategist at UBS in Melbourne.

Importers are "getting less copper units from scrap, and more from concentrate and metal," he added, noting that China's overall scrap crackdown looked set to continue with additional restrictions to come into force in July.

Annual copper concentrate imports rose 13.7 percent in 2018 year-on-year to a record 19.72 million tonnes, although December imports fell by 13.4 percent from November to 1.46 million tonnes, the lowest since February 2018.

(By Tom Daly and Melanie Burton; Editing by Christian Schmollinger)