AMSTERDAM, Netherlands - ABN Amro's management faced attacks on two fronts yesterday as a takeover attempt led by the Royal Bank of Scotland turned hostile and a shareholder-rights group sued to block an acquisition by Barclays that ABN Amro's board had approved.

The developments heightened the crisis atmosphere around the Dutch bank, which is at the center of the largest takeover struggle in the history of the financial industry, with as much as $100 billion at stake.

Royal Bank of Scotland, together with its allies, Spain's Banco Santander Central Hispano SA and Belgian-Dutch bank Fortis NV, said they had been pushed to bypass ABN's boards by "the terms of the contract ABN Amro has signed with Bank of America," referring to a deal ABN Amro unveiled Monday to sell its U.S. arm, LaSalle Bank Corp., to Bank of America for $21 billion as part of its agreement with Barclays.

That move was widely seen as a poison-pill measure to frustrate the Royal Bank consortium, which also wants LaSalle, and it drew enraged reactions from shareholders at ABN's chaotic annual shareholders meeting Thursday. Analysts believe that Barclays' all-share bid will be worth at least 10 percent less than Royal Bank's proposed cash-and-share bid of 39 euros a share, which values ABN at 72.2 billion euros ($98.1 billion).

The Royal Bank of Scotland is the parent of Citizens Financial Group, which owns Citizens Bank of Pennsylvania. Banco Santander owns about 25 percent of the shares in Sovereign Bancorp Inc. of Wyomissing, Pa.