Copper hit its lowest level in more than 3-1/2 years on Wednesday on worries about growth and tighter credit in China, while aluminium sank as market data highlighted the metal's chronic oversupply.
Three-month copper on the London Metal Exchange touched $6,325.75 a tonne, its lowest level since July 2010. It earlier traded down 0.72 percent in official midday rings to $6,436 a tonne.
The looming bankruptcy of a Chinese developer owing billions of yuan to domestic banks has again raised credit worries in China after this month's first ever bond default from a private company.
"They (credit fears) are rumbling along there doing more damage," said BNP Paribas analyst Stephen Briggs.
He added that while last week's fears that China's copper financing deals would unravel were overdone, they remain a concern. "The credit concerns call into question the scope for increased financing deals in a year which the market is likely to be in surplus," he said.
Still, there is no sign yet that defaults have sparked upheaval in the country's credit markets or that China's frothy real estate market is about to melt down, even if investors are watching nervously.
In industry news, Jinchuan Group, China's third-largest copper producer, declared force majeure on some copper concentrate purchases after a technical problem that will keep it from hitting a 2014 target of about 400,000 tonnes of copper.
In other metals, aluminium fell 1.18 percent in rings to trade at $1,715.50 a tonne. The contract also hit a month low at $1,704.25 a tonne.
London Metal Exchange data out earlier showed aluminium stocks held in warehouses shot up by 280,000 tonnes in one day to touch 5.435 million tonnes, taking them firmly back near recent record highs.
Earlier, the aluminium contract in Shanghai hit its lowest since its 2005 inception, weighed down by oversupply, and as tighter credit in China takes a toll on demand.
In the wider markets, world stocks slipped as military tensions between Ukraine and Russia ratcheted up, while the dollar held firm, drawing comfort from expectations the Federal Reserve will further unwind monetary stimulus.
A stronger dollar makes dollar-priced metals more costly for non-U.S. investors. New Federal Reserve chair Janet Yellen will address a news conference later in the day, at the end of the central bank's two day policy meeting.
Elsewhere, worries about Western sanctions against Russia for its move to annex the Crimea region in Ukraine, combined with a halt to Indonesian ore supplies spurred LME nickel prices to an 11-month peak of $16,385 a tonne.
Nickel later traded down 0.28 percent in rings to $16,145 a tonne.
China's supplies could potentially be cut further thanks to the production problem at Jinchuan, the country's top nickel producer.
Lead traded down 0.41 percent at $2,061 a tonne, zinc was last bid down 0.86 percent at $1,962, while tin traded up 0.24 percent at $23,225.
The global lead market was in deficit by 31,000 tonnes in January, while the global zinc market was in a 61,000 tonne deficit, a monthly bulletin from Lisbon-based International Lead and Zinc Study Group (ILZSG) showed on Wednesday.