Shares in Rightmove, the online property portal, have risen sharply on confirmation of bid interest from an Australian rival majority-owned by Rupert Murdoch's News Corp.
REA Group said early on Monday it was considering a takeover proposal to create a globally-focused real estate company.
Any bid would likely comprise a cash and shares offer. No approach has been made to date, REA said.
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REA is 61%-owned by News Corp, which has existing UK interests including The Sun and The Times newspaper brands under the company's News UK arm.
Shares in Rightmove jumped 24% to 689p when the FTSE 100 opened for business, taking them to their highest level in two-and-a-half years.
Rightmove, which makes money from listing real estate agents on its website, had a market value of almost £4.4bn as of Friday's close.
Analysts at Investec in a note agreed with REA's stand, the Reuters news agency reported, that the offer and the enlarged group presents a highly attractive investment opportunity given an easing interest rate environment in the UK and recent new investment starting to pay off.
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REA stock, however, fell 8%.
Under the UK's takeover code, it has to update the market if it has a firm intention to make a bid by 30 September.
Rightmove was yet to comment.
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