Centrica has announced on Monday the purchase of one million Centrica ordinary shares through Goldman Sachs International at an average price of 307.161p per share.The highest price and the lowest price paid for these shares were 308p and 306p respectively.The purchased shares will be held as treasury shares.As of Monday, Centrica holds 59,433,480 ordinary shares in treasury along with 5,000,494,801 ordinary shares in issue.Following the announcement, Centrica's share price fell 0.62% to 305p at 9:18 on Monday.