Kohl's Corp on Friday adopted a shareholder rights plans to protect itself from hostile takeovers, days after receiving buyout offers that the retailer said undervalued it.

Last month, activist investor Starboard Value-backed Acacia Research Corp offered to buy the department-store chain for $64 a share, valuing it at roughly $9 billion.

Around the same time, sources told Reuters that Sycamore Partners was also preparing an all-cash offer for Kohl's at $65 per share.

Without naming its suitors, Kohl's said on Thursday the offers did not adequately reflect its future growth and cash flow generation. It has hired Goldman Sachs to engage in talks with interested parties about a potential sale.

Activist investors Macellum Advisors and Engine Capital, unhappy with Kohl's performance, have been pressuring it to explore options including a sale.

Macellum, which owns nearly 5% of Kohl's stock, said it was "disappointed and shocked" by the company's decision. It added that the board is taking "unprecedented" steps to douse growing takeover interest.

Shares of the company rose 1%, adding on to a 25% gain over the past two weeks on news of the offers. It had a market value of $8.15 billion as of Thursday's close, according to Refinitiv.

Morningstar analysts said it is "risky" to reject credible offers, especially after unfavorable market conditions for Kohl's in 2021.

The company also said the shareholder rights plan, popularly known as a "poison pill", expires in February 2023. The rights will be exercisable if a person or group, other than passive institutional investors, acquires a stake of 10% or more.

Poison pills make a proposed takeover more expensive or difficult by allowing existing shareholders to buy additional shares at a discount, diluting a hostile suitor's ownership stake.

Sycamore declined to comment and Acacia did not respond to a request for comment.