Wall Street's main indexes were subdued at the open on Wednesday, following a tech-led selloff in the previous session over surging valuation concerns.

At the opening bell, Wall Street's main indexes were muted: the Dow Jones Industrial Average rose 0.03 per cent to 47,097.31, the S&P 500 fell 0.03 per cent to 6,769.77, while the Nasdaq Composite rose 0.04 per cent to 23,358.075.

But selling extended into a second day on Wednesday in global markets, leaving those in Seoul and Tokyo around five per cent beneath peaks reached on Tuesday morning.

Falls in technology stock prices from the day before are cause for caution but not panic yet, say brokers and investors who have been riding a runaway market to record highs and some stretched valuations.

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