• Sterling falls 10 pct to lowest since before 1985 Plaza Accord
• Yen slips as Japan hints at possible action
•  SNB confirms intervention, Swiss franc off highs

The euro fell to $1.0912, a low last seen in March, before recovering to $1.1050, still down 2.9 percent on the day. It fell nearly 2 percent against the franc, before recovering to trade 1.1 percent lower at 1.0891 francs.

Demand for the safe-haven yen has grown steadily with Brexit anxiety over the past month. The greenback dropped to as low as 99 yen, a fall of 6.7 percent, before gaining to 102.40 yen, still on track for its biggest one-day drop since late 1998.

The rise in the yen kept alive the risk of intervention by the Japanese and perhaps even coordinated intervention by the Group of Seven countries in coming weeks.

"In the next week or two, it would be naive not to expect central banks to be in the market trying to smooth price movements," said Stewart Richardson, chief investment manager at RMG Wealth Management, adding investors are likely to stay away from riskier currencies and volatility was likely to surge.