Microsoft is suing Samsung for threatening to stop paying royalties to the software giant for patents behind the Android operating system.

Microsoft posted its first quarterly loss in its 26 years as a public company as it declared a struggling online ad business a bust and prepared for one of the biggest product updates in its history.

Microsoft Corp, responding to reports that it is failing to abide by its antitrust agreement with the US government, said it is committed to "vigorously enforcing" the pact.