Investors swapped out of US equity funds and into bonds at the fastest clip on record last week, according to Lipper Inc., as they grasped for safety while the stock market swooned.

Traditional US stock mutual funds and exchange-traded funds together saw withdrawals of $18.8 billion in the week ended Feb. 5, their biggest weekly withdrawals on record. The abrupt reversal, led by ETFs, comes after US stock funds attracted $172 billion in 2013, the biggest inflow since the financial crisis.