Finnish telecommunications equipment maker Nokia reported a first-quarter net loss of 513 million euros (583 million dollars) on Tuesday in its first report since acquiring rival Alcatel-Lucent of France in January.
Nokia had reported a net profit of 177 million euros in the first quarter of 2015, when it was a standalone company.
First-quarter combined net sales fell to 5.6 billion euros from 6.1 billion euros a year ago on a comparable combined company basis, amid lower investments by mobile operators, Nokia said.
Although the decline was "disappointing," chief executive Rajeev Suri said it was not "a surprise" and noted the company had cautioned about "market headwinds" in its fourth-quarter report.
Nokia was the world's leading mobile phone maker until smartphones from Apple and companies using Google's Android operating system overtook it.
After it sold its loss-making handset business in 2014 to US software giant Microsoft, the Finnish company has said it would focus on providing broadband infrastructure software and services.