Aluminium prices hit their highest in six weeks on Thursday as fund buying returned after one-day pause, spurred by concern over tight supply.

Three-month aluminium on the London Metal Exchange rose 1.1% to $2,513 a metric ton by 1028 GMT, having touched $2,531 for its highest since July 9, breaking above the 100-day moving average at $2,496.

Funds known as commodity trading advisors (CTAs), which are largely driven by computer programs, resumed buying after aluminium registered a slight intraday gain on Wednesday, one trader said.

Prices of the metal used in transportation, construction and packaging are on track for a 6% gain this week, the strongest weekly growth in four months, against a backdrop of higher demand for alumina, the intermediate product between bauxite and aluminium, and tight supply of bauxite.

Commodities markets are also keeping an eye on Canada, where rail freight could come to a grinding halt after the country's two biggest railroad operators announced simultaneous work stoppages over labour contracts.

Canada is the largest aluminium supplier to the United States, but the aluminium premiums paid above the LME benchmark by U.S. buyers have been steady so far.

Meanwhile, LME zinc was up 1% at $2,878 a ton after hitting $2,882 for its highest since July 17.

Large Chinese zinc smelters have agreed to adjust planned maintenance on production lines and postpone commissioning of new capacity as falling ore processing prices have eroded profits.

In other metals, LME copper fell 0.5% to $9,213 a ton, lead was up 0.3% at $2,090.50, tin added 0.6% to $32,875 and nickel lost 1.2% to $16,710.

(Reporting by Polina Devitt in London; Additional reporting by Mai Nguyen in Hanoi Editing by David Goodman)