Independent News & Media has bought PropertyNews.com, the Northern Ireland property website which has recently expanded into the Republic.
The company did not say how much it had paid for the business but it is believed to be €5-€10 million.
PropertyNews.com, which was launched in 1998, is headed by its founder Graham Brown and its chief executive Conor MacCarrick, who will continue to run the group. Independent has also acquired the Property-News monthly newspaper, a freesheet founded by Mr Brown and his wife Lorna in 1983.
The deal is conditional on regulatory approval.
Last May, PropertyNews.com began to expand into the Republic of Ireland. It claims a market share of 70 per cent in Donegal and an estimated 25 per cent across 10 other counties in the border and midlands region.
In total, the company's database lists nearly 20,000 properties for sale, 4,000 of them in the Republic. It says that 99 per cent of estate agents in Northern Ireland list their properties on the site and it estimates that about 90 per cent of all properties for sale in Northern Ireland at any given time are shown.
Site traffic on Property-News.com reached 10 million page impressions in February, making it the most popular website in Northern Ireland.
Unlike similar sites in the Republic, it is cheap to advertise on PropertyNews.com. To list a property costs around £12.50 (€18.18) compared to €100-€200 on the myhome.ie site in the Republic.
Under Independent's ownership, the company plans to continue its expansion in the Republic and to also look toward the British market.
"The formula which made PropertyNews.com so successful in Northern Ireland is now being rolled out across the Republic and the strength of the Independent newspaper titles will considerably accelerate this," Independent's chief executive Sir Anthony O'Reilly said.
He noted the acquisition was part of the company's strategy of becoming "the number one classified website in every market in which it operates".
Independent, which reported 2005 results last week, set out plans for further global expansion. Aside from eastern Europe, where it is 60-70 per cent of the way toward doing a deal, and Australia, building its online business is a priority for the group.
Last week, it took a 20 per cent stake in British gaming company Cashcade. It has also been linked with a possible bid for the Irish internet portals myhome.ie and daft.ie.
But analysts said that yesterday's announcement suggested it might no longer be interested in making such a purchase, choosing to focus on using its extensive media interests to expand the PropertyNews.com business organically in the Republic. However, sources close to the company declined to rule it in or out as a likely bidder.
Shares in Independent added two cent to close at €2.57 last night.