OSLO, Dec 3 (Reuters) - Norwegian real estate firm Entra said on Friday it had agreed to buy rival Oslo Areal for 13.55 billion Norwegian crowns ($1.48 billion), in the latest twist of consolidation in the Nordic real estate sector.

Entra is itself subject to a $4.1 billion bid from Swedish rival Balder, with a deadline for owners to accept or reject the offer by Dec. 7, but it remains unclear if that takeover will succeed.

Oslo Areal's joint owners, Norwegian insurer Gjensidige and Swedish pension provider AMF Pensionsforsakring, in late October said they were contemplating a sale of the firm, of which they each own 50%.

"This transaction enables additional profitable growth and increased shareholder values in Entra going forward by utilising our strong balance sheet," the chair of Entra's board, Siri Hatlen, said in a statement.

Sweden's Balder holds a 34% stake in Entra, and the board of the Norwegian firm has recommended its owners to accept Balder's bid or sell their stock on the open market.

But Entra's other major shareholder, Swedish real estate firm Castellum, has not said whether it will divest its 30.6% stake.

Both Castellum and Sweden's SBB have previously attempted to buy Entra.

Castellum recently bought Swedish competitor Kungsleden in a deal worth $3.1 billion.

Gjensidige said it will book a profit of about 2 billion Norwegian crowns from the sale of its stake in Oslo Areal.

($1 = 9.1395 Norwegian crowns) (Reporting by Terje Solsvik, editing by Gwladys Fouche)