S Immo said Immofinanz's offer price was well below S Immo's net asset value and did not take into account the value analysis of its property portfolio it had conducted last month.

Discussions over a tie-up between the two companies have been ongoing for years. In 2019, they abandoned talks after failing to agree on a share exchange ratio.

Analysts have long said consolidation among Austria's three remaining listed property groups, which also include CA Immo, would make sense as it would increase their collective sales power and financial strength.

The 22.25 euro per share offer is subject to the condition that S Immo cancels its current policy limiting its shareholders' voting rights to 15%, even if their stakes are higher, Immofinanz said.

Immofinanz - which already owns 26.5% of S Immo but wants to gain a controlling stake to strengthen its business and make savings - has failed to overturn that policy in the past.

The minimum acceptance threshold for the offer is 50% plus one share, Immofinanz said, with the acceptance period running from May 19 to July 16.

"S Immo's management will examine the offer documents from Immofinanz in detail and issue a statement for the shareholders," a spokeswoman for S Immo said.

(Reporting by Veronica Snoj and Zuzanna Szymanska in Gdansk; Editing by Jan Harvey)