International Business Machines Corp. (IBM) kicked off a debt offering that's likely to make this the corporate-bond market's busiest week in at least eight months, a rare buying frenzy amid turbulent markets globally.

The computer-services giant plans to sell senior unsecured bonds in as many as eight parts to help fund its $33 billion acquisition of Red Hat Inc., according to a person with knowledge of the matter. The longest portion of the offering, a 30-year security, may yield around 1.55 percentage points more than Treasuries, said the person, who asked not to be identified as the details are private.

IBM is starting the bond sale just days after receiving U.S. regulatory approval of the of Red Hat purchase. The company said it's working with competition authorities in other jurisdictions—European Commission clearance is outstanding—though IBM still expects the transaction to close in the second half of this year.