** Shares in BIM Birlesik Magazalar BIMAS.IS, Migros Ticaret MGROS.IS, Sok Marketler SOKM.IS slide after Turkey's competition authority has launched investigations into the Turkish retailers
** BIM said Turkey's Competition Board has launched two separate investigations into it and several other retail companies and their suppliers
** Migros, Sok Marketler and Carrefoursa Carrefour CRFSA.IS also said the watchdog had decided to open an investigation to determine whether certain retailers, suppliers, and manufacturers, including their own companies, had violated relevant articles of the Law on the Protection of Competition
** Serhat Baskurt, algorithmic operations manager at brokerage ALB Yatirim, says investigation led to sell-off at market open
** When asked about the potential impact on other companies under investigation, Baskurt noted the increasing frequency of investigation and growing regulatory pressure on the sector would have a negative effect
** Shares in BIM and Migros drop almost 5% and are worst performers on Turkey's main BIST 100 index .XU100, Sok Marketler drops 2.58%
** Shares in Carrefoursa Carrefour is up 0.65%
(Reporting by Canan Sevgili)
((canan.sevgili@thomsonreuters.com))