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U.S. stock index futures screamed lower, with Dow futures tumbling as much as 350 points, as fears surrounding the health of China's economy multiplied.

These concerns saw the benchmark Shanghai Composite index notch up its biggest one-day percentage loss since 2007 on Monday, closing down 8.5 percent.

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Panic spread to European markets, with the pan-European FTSEurofirst 300 down over 3 percent in early London trading. All major bourses were off a similar amount. The index has shed over $1 trillion in market value in August so far.

The slide comes after U.S. stocks closed deep in the red on Friday, pushing the Dow and Nasdaq into correction territory. The major averages had their biggest trade volume day of the year and posted their worst week in four years.