In a statement, the group's deputy chief executive Massimo Capuano said the transfer represents a "major step" towards the integration of the London Stock Exchange and the Milan-based exchange Borsa Italiana.
A total of 320 MTA stocks and 40 listings from Expandi index started trading on TradElect on Monday (November 10th).
Other Italian markets currently hosted on the Affari trading platform will transfer to TradElect in the first half of next year, the group added.
"In creating Europe's largest pool of liquidity, we anticipate that the group's network of 500 equity trading members will drive tighter spreads and a lower cost of capital, to the benefit of investors and companies," Mr Capuano said.
In related news, the LSE Group has today (November 13th) posted a 57 per cent increase in its first-half operating profits before exceptionals and other considerations to Â£179.9 million.