Share trading on the London Stock Exchange
As a result, all order-driven securities were placed in an auction call period at 1038 GMT (5:38 a.m. EST), with all share prices currently to be considered indicative, he added.
The FTSE 100 <.FTSE> index level frozen at 5,264.97, down 99.84 points, or 1.9 percent, and whilst the FTSE 250 value is changing, this is due to exchange rate movements rather than price changes, the LSE said in a service alert.
In addition, the distribution of all FTSE UK Series real-time index values is also affected, the bourse operator said.
The length of the auction call period has not yet been decided, however, a minimum of 30 minutes notice will be provided ahead of the scheduled uncrossing time, LSE added.
In September last year the LSE suffered its worst systems failure in eight years, causing the share market to suspend trading for about seven hours and infuriating its users.
(Reporting by Jon Hopkins, additional reporting by Harpreet Bhal)