BEIJING: Chinese coking coal futures extended gains into a third session on Monday, jumping as much as 6.2% as lower imports, sliding inventories and mines starting maintenance activity stoked supply concerns.

"Coal mines in major production areas had mostly finished their targets at year-end and started maintenance for an estimated three-five days," GF Futures wrote in a note.

Coking coal inventories at coke plants and steel mills slipped to 18.36 million tonnes as of Dec. 25 from 18.49 million tonnes a week earlier, according to Mysteel consultancy.

Adding to supply worries, China's imports of the key steelmaking ingredient plunged nearly 37% to 3.7 million tonnes last month from October, data from the customs office showed.

The most-traded coking coal futures on the Dalian Commodity Exchange, for May delivery, closed up 4.2% at 1,713 yuan ($262.29) per tonne, after hitting a high of 1,745 yuan in early trade.

Coke futures also gained, settling 1.6% higher at 2,836 yuan a tonne.

Dalian iron ore futures slipped 0.7% to 1,026 yuan a tonne, following spot 62% iron ore prices which fell to $166 per tonne on Friday.

Construction steel rebar on the Shanghai Futures Exchange fell 0.7% to 4,244 yuan a tonne.

Hot rolled coil dropped 2.5% to 4,418 yuan per tonne.

Shanghai stainless steel futures, for February delivery, gained 0.2% to 13,595 yuan a tonne.

Malaysia has imposed provisional duties on certain cold-rolled stainless steel imports from Indonesia and Vietnam, pending the conclusion of an anti-dumping investigation, its Ministry of International Trade and Industry said.

Profits at China's industrial firms grew robustly in November for a seventh month of gains, supported by strong industrial production and sales, as manufacturers continue their recovery from the COVID-19 downturn.