The number of put option contracts on equity market indices, which give investors the right to sell at a predetermined price within a given time period, rose by 60% yesterday as several global stock markets posted their greatest one-day losses since September 11, 2001 and investors sought protection from further price falls.

Data from futures and options exchange Eurex shows 2.4 million put option contracts on equity market indexes traded yesterday, up from 1.5 million last Friday. The average daily volume of contracts for the month to January 21 was 1.2 million.