Chinese spot alumina prices made further gains on Thursday on the back of record high prices in the global market this week due to supply concerns.

The Platts ex-works Shanxi daily spot alumina assessment rose Yuan 70/mt ($11) to Yuan 2,970/mt cash on Thursday, as the bid-ask spread increased to Yuan 2,950-3,000/mt from a previous Yuan 2,850-2950/mt.

The current price was up Yuan 220/mt on the week, and also reflected a rise of Yuan 270/mt from last month.

The Platts Australian alumina daily assessment stood unchanged at $710/mt FOB on Thursday, but had surged $160/mt on Wednesday after a 30,000 mt Brazilian cargo was reportedly traded at $800/mt FOB with 30 days credit.

On Thursday, Aluminium Corp of China (Chalco) raised their official list price to Yuan 3,500/mt cash from Yuan 3,250/mt on Wednesday.

No trades were reported at the higher levels, but domestic sentiment firmed further, and numerous refiners held back offers in anticipation of even more gains.

"Considering FOB prices now, Chalco's latest offer at Yuan 3,500/mt is not too high," a Shanxi refiner said.

"We heard someone has sold at Yuan 3,200/mt spot for export, but it's not confirmed," he added.

"Chalco has raised offers several times to support prices. It's very understandable especially when the market has such high expectations for prices now," a northwest China smelter said.

Prices are generally expected to continue testing higher in the near term, heading towards the Yuan 3,500/mt level, sources said, citing cuts at Hydro's Brazilian Alunorte refinery and the Rusal sanctions as the main supporting factors.

"Both are not likely to be resolved soon, so tightness in the global market will continue. If they remain shut for a long period, then the sky's the limit for prices, we cannot even imagine right now," a Shanghai trader said.

Another Chinese trader agreed, adding that "everything is policy driven now, so it's hard to predict."

Stronger domestic aluminum prices currently also added support to alumina, sources added.

The front-month primary aluminum contract on the Shanghai Futures Exchange breached Yuan 15,000/mt to close at Yuan 15,285/mt on Thursday, up from Yuan 14,275/mt last week, and also from Yuan 13,870/mt a month ago.