UPDATE 2-LSEG investors Thomson Reuters, Blackstone to sell $2.9 bln shares in bourse operator

(Adds CPPIB declined to comment in paragraph 5)

Sept 6 (Reuters) - Investors in the London Stock Exchange Group, including Blackstone and Thomson Reuters , are launching a sale of roughly 28.3 million shares worth about 2.3 billion pounds ($2.9 billion), bookrunners for the deal said on Wednesday.

This follows a sale in May of about $3.4 billion shares in the bourse operator as the investor group seeks to offload its stake in LSEG.

The consortium, which includes Canada's CPPIB and Singapore's GIC, aims to sell a total of about 43.1 million shares over time in LSEG through the offering, a directed buyback and a sale of call options, bookrunners said.

LSEG separately said it plans to buy back about 750 million pounds worth of limited-voting ordinary shares through an off-the-market purchase.

Thomson Reuters, Blackstone, and GIC did not immediately respond to requests for comment. CPPIB declined to comment.

The consortium holds about an 18.7% economic interest and an 11.3% voting interest in LSEG. Following the completion of the latest deals, the group's remaining voting shares and limited-voting ordinary shares will be under a 180-day lock-up period.

Thomson Reuters, parent of Reuters News, holds a minority stake in LSEG. Thomson Reuters and Blackstone had sold financial data firm Refinitiv to the bourse operator in 2021. ($1 = 0.8002 pounds) (Reporting by Pushkala Aripaka and Amna Karimi in Bengaluru; Editing by Sriraj Kalluvila and Arun Koyyur)