Short-seller Hindenburg Research said Wednesday it had taken a long position in Twitter Inc. (TWTR) shares and warned the social media firm's lawsuit against Elon Musk, the world's richest man, could pose a threat to his companies.

Twitter's shares rose about 6% to $35.90 on the news, a day after the company sued Musk for violating his $44 billion deal and asked a Delaware court to order him to complete the merger at the agreed $54.20 per Twitter share.

Musk, who is the chief executive officer at Tesla Inc and heads SpaceX, said on Friday he was terminating the deal because Twitter violated the agreement by failing to respond to requests for information regarding fake or spam accounts on the platform.

Hindenburg did not elaborate on the threat the lawsuit poses to Musk, but legal experts have said that from the information that is public Twitter would appear to have the upper hand.

"We have accumulated a significant long position in shares of Twitter. Twitter's complaint poses a credible threat to Musk's empire," Hindenburg said in a tweet.

Twitter was not immediately available for a comment.

The legal face-off is the latest twist in the months long saga that began after Musk in April bought a stake in Twitter and later offered to buy the company.

Then in May, he put the buyout on hold until Twitter proved that spam bots account for less than 5% of its total users, even as he had gathered investors to fund a portion of his deal.

Hindenburg, which earlier had a short position, had said in May that Musk's offer could get repriced lower if he walked away from the deal.