Carl Icahn, the billionaire corporate raider seeking to force a sale of Yahoo!, has become the target of a raid himself after rejecting a $4.5 billion takeover offer for his drugs company, Imclone.

Mr Icahn, who is chairman of the cancer drug company, said that he and the rest of the board had decided to reject the buy-out offer from Bristol-Myers Squibb, the pharmaceuticals giant, claiming that the approach is too low.

Bristol-Myers had offered to buy Imclone, a group which is developing a cancer treatment called Erbitux, for $60 a share, representing a 30 per cent premium to Imclone stock before the approach was made.

Mr Icahn, who is one of Imclone's biggest shareholders, was appointed to the board two years ago after a proxy fight that led to the incumbent chief executive, Joseph Fischer, to leave. Mr Icahn became chairman, ousted another four directors and appointed his own chief executive, John Johnson, last year.

In May, Mr Icahn pursued a similar strategy with Yahoo!, the internet search engine, buying up a 5 per cent stake and threatening to remove all directors from the board, and planning to install himself and allies to handle a sale of the company. In the event, Yahoo! sought a truce last month and offered Mr Icahn and two of his own nominated candidates board seats at the Silicon Valley based company.

Yesterday, Imclone issued a statement rejecting the offer from Bristol-Myers Squibb, with whom it has a partnership deal for the development of Erbitux, a treatment for colon and head and neck cancer.

In the statement, Imclone said that while it had formed a committee to evaluate the offer, it was considering splitting the company into two parts instead. It also said that Mr Icahn was "disturbed" that Bristol-Myers Squibb may have known about confidential proposals to divide Imclone through the dual relationship of one of the company's own board directors.

Yesterday, Mr Icahn claimed that he had the public support of a number of Imclone investors.

The statement said: "ImClone indicated that other large stockholders of the Company have given statements to the press indicating their opposition to the Bristol-Myers offer."

Shares in Imclone fell 2 per cent to $64.22, still well above the Bristol-Myers Squibb $60 a share offer. Yesterday's price indicates that Wall Street believes that Mr Icahn will either succeed in extracting a higher price for the cancer drug company or that it will proceed with plans to divide itself into two.

A spokesman for Imclone failed to return calls yesterday.

Separately, WCI Communities, a housebuilding group which is also chaired by Mr Icahn, filed for Chapter 11 bankruptcy protection yesterday. In a statement, the Florida based company said it had replaced its chief executive. The company has been seeking, and failing to raise new funding.

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