One of Alibaba's (BABA - Get Report) biggest shareholders, Softbank, said on Wednesday in Tokyo that it will sell at least $7.9 billion of its shares in the Chinese e-commerce giant to reduce its debt.

Alibaba's shares fell 2.7% in after-hours trading on Tuesday and were down 2.7% in pre-market trading on Wednesday. The stock had closed in New York at $81.91 on Tuesday.

Softbank, the Japanese telecom investor which owns most  of Sprint (S - Get Report) , held 32.2% of Alibaba's issued and outstanding shares at the end of March. The sale will bring the stake to about 28%. Softbank has agreed with Alibaba not to transfer any further shares for a six-month period.

The telecom said the transaction was "driven purely by [Softbank's] capital structure and de-leveraging objectives." The sale will allow Softbank to build up a liquidity cushion and improve the company's debt-to-earnings ratio.

In a statement Softbank's chairman and CEO Masayoshi Son said that there would be a continued partnership between the two companies.

"This investment has been phenomenally successful, and over the past 16 years, we have built a close relationship, working together on many exciting projects. In that time, we have not sold any Alibaba shares," he said.

Softbank was up 0.4% in trading in Tokyo on Wednesday.  

Alibaba on Tuesday said the Securities and Exchange Commission is investigating its accounting practices. It said it was cooperating with regulators and noted that it was told the review wasn't an indication it had violated securities law.