Feb 13 (Reuters) - Castellum has increased its

shareholding in Entra ( ENTOF ) to more than a third of all its

shares and will make a mandatory offer for the Norwegian real

estate firm, it said on Thursday.

The Swedish real estate group bought further 100 shares in

Entra ( ENTOF ) for 110.40 Norwegian crowns per share, crossing the

threshold for a mandatory offer for the remaining shares, it

said in a statement.

Castellum said that Entra's ( ENTOF ) largest shareholder Fastighets

AB Balder, which controls nearly 40% of the Norwegian

firm's shares and votes, has said it will not accept Castellum's

offer.

Balder said in a separate statement that it did not intend

to make a counteroffer.

Carlsquare analyst Bertil Nilsson said the market reaction

was likely to be limited as Balder would retain its stake in

Entra ( ENTOF ) despite Castellum's offer.

"However, there is likely to be speculation in Entra's ( ENTOF ) shares

about a long-term takeover of the company by either Castellum or

Balder," Nilsson added.