The growing possibility that the U.K. might leave the European Union shook markets globally on Monday, reflecting broad concern that next week’s referendum could slow down the world’s economy.

Polls suggest that momentum is growing for a vote on June 23 for Britain to leave the EU, spurring concerns about a prolonged stretch of uncertainty that could damage economic growth and trigger losses in financial markets. Stocks slumped, Japan’s yen surged and bond yields tumbled to fresh lows in a broad flight to safety.

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