Prices of oil, base metals and precious metals were slashed on Thursday afternoon as cross-asset profit-taking kicked in, traders said.

Silver was first to begin falling and soon dragged other commodities with it.

Gold was quoted at $620.30/621 per ounce at 1549 GMT, down almost 4 percent from the 25-year high of $645.75 it made earlier in the day.

Silver was quoted at $12.90/13.10 at 1554 GMT, down from its high of $14.68.

It is cross-commodity profit-taking. Silver is in free-fall. Silver initially led gold down then gold got its own momentum. If gold holds above $620 then there could be a recovery but if not people will be running for cover, said a trader as the sell-off began.

Brent crude traded down at $72.83 per barrel at 1550 GMT from its earlier high of $74.22, and copper was at $6,260/6,270 a tonne, down from Wednesday's close of $6,390.

A fund source was quick to point out that the selling was profit-taking rather than the start of a large-scale exit of funds from commodities.

A $100 move up or a $200 down (in copper) is not big news any more. Other commodities are down and the selling is related to that, he said.

If someone starts to buy, the pattern will quickly reverse. It pays to keep an eye on other products such as silver and gold as base metals will move the same way, he said.

A bout of profit-taking had been expected after prices across commodities had repeatedly hit new highs.

Much of the new speculative investment in precious metals and oil has been encouraged by worries about the nuclear standoff in Iran.

There is new money coming into gold, a European fund manager with long positions in energy and precious metals said earlier in the day.

When prices go up as quickly as they are now people can be more cautious, but the analysts keep (forecasting) astronomical figures and there are still some big unknowns -- like Iran -- so people are still ready to bet that the rise is not over.

On Wednesday, a senior U.S. official spoke of a greater sense of urgency to curb Iran's nuclear ambitions.

On Tuesday the United States failed to secure international support for sanctions against Iran and President George W. Bush refused to rule out nuclear strikes if diplomacy failed to curb the country's atomic program.

MINING SHARES

Shares in mining companies, which have risen in step with commodities prices, were knocked by Thursday's sell-off.

Rio Tinto shares (RIO.AX)(RIO.L) lost 3 percent to trade at 3065 pence in London at 1539 GMT, down from 3158 two hours earlier, but still up 13 percent since the start of the year.

Rival BHP Billiton (BHP.AX)(BHP.L) was at 1149, down from 1184, but still up 19 percent.

Rio Tinto earlier on Thursday said it had been working flat out to boost output and so cash in on high prices

The diversified miner was expected to make net profit of $6.5 billion in 2006.

Precious metal