The company says Bloomberg, set up by New York Mayor Michael Bloomberg, intruded upon three of its patents, for which it must pay "injustive relief" and damages.

"Reuters has invested millions in research and developement to develop the best automated trading technologies to the market," a spokesman said.

"It cannot allow an unauthorised use of its intellectual property."

Tough times

Reuters decided on court action after fruitless talks with Bloomberg, its main rival on the US market.

The lawsuit is the latest indication of the tense competitive situation on the trading technology market, which lies at the heart of both firms' business.

Reuters was born as a news organisation, but has shifted heavily towards the once-lucrative technology sector in recent years.

Bloomberg, a younger company, was the most aggressive in marketing itself as a systems supplier, and now has a dominant share in certain key markets, notably bond trading.