Microsoft Corp said it will hold a press conference on Thursday for a significant company announcement, but the software maker said the news was not related to its $42 billion offer for Yahoo Inc.

The company will hold a conference call at 11.30 a.m. EST with Chief Executive Steve Ballmer, chief software architect Ray Ozzie, senior vice president of server and tools Bob Muglia and general counsel Brad Smith.

Further details were not disclosed.

Microsoft shares rose 1.2 percent in premarket trading to $28.56 from its close of $28.22 on the Nasdaq on Wednesday.