High-frequency trading firm Optiver made over half of its revenues from outside the EU for the first time in its history last year, as European regulators take a hardline stance towards high-speed trading.

The Dutch group, one of the world's largest HFT firms, said today that its total trading revenues fell 24% to €370.1m for the year ended December 31, 2012, according to its annual report. The group's net trading profits fell 11.4% to €141.6m.