Ericsson has posted a third-quarter net loss of £262m as sales fell 19%.
The loss compared with a net income of £290m in the same period last year.
Sales were £3.6bn.
The company also said Chairman Lars Ramqvist will not seek re-election at next year's annual general meeting.
He would be replaced with Electrolux chief executive Michael Treschow, pending shareholder approval.
Ericsson has unveiled its results early after some of the figures were leaked to the media. Ericsson said it was investigating the leak.
The company said sales in its key network equipment division were down 11% year-on-year to £2.8bn.
The systems unit made a slight operating profit, with a margin of 1% but the company warned that market conditions would remain difficult.
Ericsson had warned in late September that it saw conditions in its key systems market deteriorating but had not provided any detailed guidance.
Its net loss for the full nine month period was £1.1bn, compared with a net profit of £1.2m in the previous year. Year-to-date sales fell 9% to £11.46bn from £12.66bn last year.