China's rare earth exports rose 19.2% year-on-year in March, customs data showed on Tuesday, hitting their highest since at least 2014 as a backlog of product was shipped, helping the industry rebound from a January-February slump due to the coronavirus outbreak.

Exports totalled 5 551.4 t last month, the General Administration of Customs said, up from 4 659 t/y earlier.

The March number exceeded exports in January and February 2020 combined and was the highest monthly total in records on the customs website going back to June 2014.

China is the world's dominant producer of rare earth materials, a group of 17 minerals prized for their use in consumer electronics and sophisticated military equipment.

For the first quarter overall, China's rare earth exports were down 2.3% year-on-year at 11 040.6 t.

Its output slowed sharply due to the coronavirus outbreak, which has killed more than 3 300 people in the country, with exports in January and February combined down 17.3% from a year earlier amid production shutdowns and transportation curbs.

David Merriman, a London-based manager at consultancy Roskill, said the closures and disruption after the Lunar New Year holiday, when China's virus containment measures were tightened, had led to a build-up of rare earth products at plant gates and ports in February.

"This material was awaiting shipping and now looks to have been cleared to meet customer orders," he added in an email. "Production figures at plants appear to be nothing unusual, suggesting this wasn't a spike in output, but a sudden clearing of materials through the system."

Australia's Northern Minerals, which exports heavy rare earth carbonate to China, said last month that customers had resumed operations after the initial disruption.

"Our information is that rare earth separation facilities in southern provinces of China that process heavy rare earths have restarted production after extended ... closures and there has been no discernible change in the demand for our product," MD George Bank said in a statement.