Swedish telecommunications and technology company Ericsson on Tuesday posted a first-quarter net loss of 10.9 billion kronor ($1.2 billion).
Previously announced restructuring costs and write-downs weighed strongly on results.
Ericsson reported a net profit of 2.1 billion kronor in the corresponding business period a year ago.
The company said year-on-year sales in the quarter declined 11 per cent to 46.4 billion kronor, although its mainstay division Networks delivered "a solid result," chief executive Borje Ekholm said in a statement.
The company said the mobile broadband market remained weak and investments were low in parts of Europe, Latin America and Africa.
Ekholm, a veteran board member who took the helm on January 16, said the company would step up cost-cutting measures since its current program "is not yielding sufficient results."
Ericsson has, in recent years, seen increased competition from Huawei of China and Finland's Nokia.
The Ericsson share was down about 2 per cent in early trading on the Stockholm bourse.