BENGALURU - Entities of billionaire Gautam Adani on Tuesday pledged more shares of the conglomerate's port unit as security to lenders, an exchange filing showed, amid a rout in the group's stocks following a scathing short-seller attack.

Emerging Market Investment and Flourishing Trade and Investment pledged a 2.69% stake in the Adani Ports and Special Economic Zone to Catalyst Trusteeship, which acted as a security trustee on behalf of lenders, the filing showed.

The total stake pledged by the entities in Adani Ports is now 7.79%. Earlier on Tuesday, another disclosure showed Flourishing Trade and Investment had pledged 0.56% stake in the company.

Shares of Adani Ports have plunged about 20% since Hindenburg Research's report on Jan. 24 alleging improper use of offshore tax havens and concerns about high debt. Seven listed group companies lost $65 billion in the rout.

Adani has called the claims baseless.

Around 17% of promoters' stake in Adani Ports was pledged as of December-end, according to stock exchange data. Promoters hold over 65% stake in the company.

Bloomberg News reported that Adani on Friday added about $300 million worth of shares to maintain its collateral cover for a loan made by a group of banks including Barclays Plc, after the steep selloff in shares.

Adani did not immediately respond to a Reuters request for comment.

(Reporting by Chris Thomas in Bengaluru; Editing by Krishna Chandra Eluri)