Mark Hemsley, European president of the exchange group best known for its futures and options products and which is home to the VIX volatility index, said the stocks traded were listed in Euronext's indexes in France, Belgium and the Netherlands.

"It's low volume because people are testing it out," Hemsley said. "We have a good pipeline of customers who are going to try and use it."

Turnover on the platform, dubbed Closing Cross, was tiny compared with the tens of billions of euros traded each day across Europe's major existing exchanges. But it represents the latest challenge to their market dominance.

Exchanges like Euronext, the London Stock Exchange and Deutsche Boerse have a dominant position in share trading, including during the closing auctions which take place at the end of the trading day and which are capturing an ever bigger portion of daily activity.

It is these end of day auctions which Closing Cross targets and CBOE says it will be cheaper to use, without disclosing any detail on long-term pricing.

As much as 20% of daily volume in Europe is now traded in the five-minute closing auction, up from 13% three years ago, due in part to growing popularity of passive or index-trading investment products and greater regulation.

CBOE won't charge customers to use the new product until the end of the year. Aquis has also launched a rival platform which is based on a monthly subscription.

Closing auctions have become a big revenue driver for the established exchanges, which charge more to trade in their closing auctions than during the day.

(Reporting by Josephine Mason; Editing by Tommy Wilkes and David Holmes)

By Josephine Mason