The logo of SoftBank Group Corp is displayed at SoftBank World 2017 conference in Tokyo
The logo of SoftBank Group Corp is displayed at SoftBank World 2017 conference in Tokyo, Japan, July 20, 2017.

SoftBank Group Corp unveiled a $23 billion quarterly net loss on Monday, its biggest ever, as a market sell-off upended tech stocks and shredded valuations at its sprawling Vision Fund unit.

The pain in the April-June quarter comes fresh after the closely watched Vision Fund posted a record $26 billion loss in May, when rising interest rates and political instability disrupted global markets, and could test investor willingness to stomach further big losses.

SoftBank founder and CEO Masayoshi Son has already pledged to tighten investing criteria and preserve cash to ride out the downturn and on Monday he signalled cuts to headcount at the Vision Fund, saying there were no "sacred areas".

"The world is in great confusion," Son told a briefing after the release of the results, remarking on the tech sell-off. But he acknowledged the company had invested in more start-ups than it should have and that valuations had been "in a bubble".

SoftBank also said it had authorised a share repurchase programme worth up to 400 billion yen, something that could assuage investors.

Overall, the sliding portfolio pushed SoftBank to a 3.16 trillion yen ($23.4 billion) net loss in the latest quarter - its largest loss ever. That compared with profit of 761.5 billion yen in the same period a year earlier.

The Vision Fund unit saw a $23.1 billion hit in value.

Listed investments that suffered a fall in value included robotics firm AutoStore Holdings Ltd and artificial intelligence firm SenseTime Group Inc.

SoftBank said it wrote down the value of unlisted assets across its two Vision Funds by 1.14 trillion yen. Analysts have said writedowns of these private assets were unlikely to reflect the extent of current market weakness.

To raise cash, SoftBank has exited companies including ridehailer Uber Technologies and home-selling platform Opendoor Technologies, for a total gain of $5.6 billion.

SoftBank sold Uber at an average share price of $41.47, compared to the Friday closing price of $32.01.

The second Vision Fund's stakes in 269 firms were worth $37.2 billion at end-June, compared with an acquisition cost of $48.2 billion.

Plunging initial public offering volumes and market scepticism towards money-losing startups have squeezed an important source of capital for SoftBank, which hopes to list chip designer Arm following the collapse of a sale to Nvidia.

SoftBank hasn't been the only casualty of the tech sell-off.

Hedge fund Tiger Global, which competes with "unicorn hunter" Son on deals, saw its flagship fund fall 50% in the first half of the year after it underestimated the impact of surging inflation on markets.

Berkshire Hathaway booked a $44 billion quarterly loss on its investments and derivatives, with Chief Executive Warren Buffett urging investors to ignore the fluctuations.

($1 = 134.9700 yen)