** Shares of Sigma Healthcare SIG.AX fall as much as 10.8%
to A$1.075, their lowest since Feb. 21
** Stock last down 5.8%; on track for worst session since
April 3, if current losses hold
** Australia's competition regulator flags major concerns
with Sigma Healthcare's proposed merger with retailer Chemist
Warehouse Group to form A$8.8 bln ($5.9 bln) company
** Says proposed integration across wholesale and retail
levels would limit competition in a number of markets,
jeopardising competition in the domestic pharmaceutical sector
** Co says the competition regulator's statement of issues
not unexpected and consistent with stated timeline
** Stock up 19.9% this year, as of last close
($1 = 1.5013 Australian dollars)
(Reporting by Shivangi Lahiri in Bengaluru)
((shivangi.lahiri@thomsonreuters.com))