Glencore announced that on Friday, the firm purchased over 0.4m Glencore ordinary shares at an average price of 340.85p per share.The highest price and the lowest price paid for these shares were 343.40p and 338.30p respectively.The purchased shares will be held as treasury shares.As of Monday, Centrica holds a total of 47,646,838 ordinary shares in treasury along with 13,230,758,628 ordinary shares in issue.Following the announcement, Centrica's share price fell 0.82% to 337.45p at 9:54 on Monday.