Stock futures freeze as tumble worsens

By 6:27 a.m. EDT December Dow Jones futures were down 6.2 percent, Standard & Poor's 500 futures were off 6.6 percent and Nasdaq 100 futures were down 6.6 percent.

All three contracts lost the maximum amount permissible before the start of futures trading in the United States.

"We are in a panic mode, I don't know how else to describe it and when you're in panic mode, all rational thought goes out of the window," said City Index chief market strategist Tom Hougaard.

"We've just got to let this thing rage. I think we'll see the Dow below 8,000 today."

According to Reuters data, December S&P futures hit a low of 855.20, while Dow Jones futures touched a low of 8,224 -- the lowest levels at which both contracts could trade in a session.

Jeremy Hughes, a spokesman for the Chicago Mercantile Exchange in London, said both contracts were "limit down."

"The limit is calculated at roughly 5 percent down. At that point it can't go any further down but it is still accessible and can go up again," he said.

"When the U.S. futures open in Chicago, the contract becomes available again, so (it could go) further down another 5 percent down, so 10 percent in total," he added.

A slew of profit warnings from major Asian companies already stripped more than 9 percent of Tokyo's Nikkei, while European equities fell by almost 10 percent at one point to hit their lowest since May 2003.

The MSCI global equities index lost 4.5 percent.

"There will be more margin calls today and something sinister is brewing," City Index's Hougaard said.

(Reporting by Amanda Cooper; Editing by David Holmes)