** Shares of Central Petroleum CTP.AX rise as much as 9.1% to A$0.060, their highest level since June 17
** The oil and gas producer says it will start an on-market share buyback programme September 15
** Co to buy back up to 10% of its issued capital over a 12-month period
** About 2.8 million shares change hands, 4.4 times the 30-day average of 644,473
** YTD, shares up 13.2%
(Reporting by Nichiket Sunil in Bengaluru)
((Nichiket.Sunil@thomsonreuters.com))