** Shares of Viva Energy VEA.AX set to lose 5.6% this week, the most since April 7

** On the day, stock up 0.2% at A$2.105

** Fuel retailer posts decline in first-half convenience sales with tobacco sales falling 27%

** Co attributes it to new tobacco packaging laws and continued growth in black market trade

** Sees HY unaudited group EBITDA on replacement cost $(RC)$ basis to be around A$300 mln ($192.99 mln) vs total EBITDA (RC) of A$451.7 mln last year

** Stock down 19.8% YTD

($1 = 1.5545 Australian dollars)

(Reporting by Sneha Kumar in Bengaluru)

((Sneha.kumar@thomsonreuters.com;))