Shanghai copper futures fell on Monday but backwardation widened sharply and spot prices gained, as traders anticipated that supplies of the metal would tighten.
Spot prices rose to 35,530 to 35,750 yuan ($4,393 to $4,420) a tonne, up about 90-yuan, while the spot premium to front-month futures widened to 670 yuan a tonne from about 300 yuan last week.
Warehouse inventories monitored by the Shanghai futures exchange fell by 458 tonnes last week to 42,071 tonnes, after rising the previous week.
September imports are also expected to be low, although many believe lower import volumes are offset by rising domestic production.
"The growth in stocks recently has been big in percentage terms but from a low base, so in absolute terms, stocks are still low," said a futures broker in eastern Jiangsu province.
Most-active December futures ended at 33,510 yuan a tonne on Monday, down 240 yuan, under pressure from lower London Metal Exchange futures.
Trading volume slipped to 82,324 lots, from 88,820 lots on Friday. Benchmark LME copper futures had fallen to $3,499 a tonne, down from $3,522.50 a tonne at the same time on Friday, after closing last week at its lowest level since August.
Shanghai aluminium futures also fell. The most-active November contract ended at 16,460 yuan a tonne, down 10 yuan from Friday's close, while trading volume more than halved to 2,070 lots.
Benchmark LME aluminium futures shed $31 a tonne from the close of Shanghai markets on Friday, to $1,790.50 a tonne on Monday.