DUBLIN (Reuters) - Smurfit Kappa's board reaffirmed its rejection of a takeover offer from International Paper Co after its U.S. rival revealed late on Tuesday that the bid was worth 8 billion euros (7.2 billion pounds).

International Paper offered 22 euros in cash and 0.3028 new International Paper share for each Smurfit share. Shares in the Irish company, which surged more than 18 percent on Tuesday after it flagged the approach, rose a further 4 percent to 35.2 euros by 0840 GMT.

"Smurfit Kappa notes the announcement released by International Paper Company (NYSE:IP) setting out the price of the unsolicited and highly opportunistic proposal... Shareholders are strongly advised to take no action," Smurfit Kappa said in a statement.