NEW YORK (Bloomberg) - Tyco International Ltd., the world's biggest maker of security systems, said its board authorised a $1 billion programme to buy back the company's stock.

The new authorisation adds to a $1 billion programme that was approved in September and that is nearing completion, Pembroke, Bermuda-based Tyco said yesterday in a statement.

The programme would cover about 25.7 million shares at Wednesday's closing price of $38.88. That accounts for 5.3 percent of the 482.2 million shares outstanding as of April 25. The company has repurchased about four percent of outstanding stock in fiscal 2008, which ends in September, Tyco said.