Tesla Inc.'s chief executive Musk says his company will start taking bitcoin transactions once there is reasonable clean energy usage by miners.

"When there's confirmation of reasonable (~50%) clean energy usage by miners with a positive future trend, Tesla will resume allowing bitcoin transactions," Musk said.

Magda Wierzycka, the chief executive of South African asset manager Sygnia, said earlier Musk's tweets about bitcoin prices were "market manipulation" and should have prompted an investigation by the U.S. Securities and Exchange Commission.

Tesla said in a February commission filing it had purchased $1.5 billion in bitcoin and would begin accepting bitcoin as a payment mechanism for its products.

However, in mid-May, the electric vehicle manufacturer paused bitcoin car purchases owing to concerns about how cryptocurrency mining, which requires banks of powerful computers, contributes to climate change.

Musk responded to Wierzycka's allegations of market manipulation Sunday, explaining that "Tesla sold roughly 10% of its bitcoin holdings "to confirm bitcoin could be liquidated easily without moving the market."  

According to the company's earnings report, Tesla sold $272 million in "digital assets" during the first quarter, which helped it cut operational losses by $101 million.

Musk's words about cryptocurrencies on social media frequently send prices rising or falling.

After Musk's tweet, bitcoin rose 5.1%to $37,360.63 at 18:10 GMT (14:10 ET) Sunday, adding $1,817.87 to its previous close.

Taproot, bitcoin's latest upgrade - four years after the "last civil war" upgrade - has finally been approved by cryptocurrency miners all over the world and is slated to go live in November this year, according to CNBC.

The new upgrade will increase transaction efficiency and privacy while also unlocking the potential of a fundamental component of its blockchain technology - smart contracts - which eliminates middlemen from even the most complex transactions.