Warren Buffett's Berkshire Hathaway Inc(BRKa.N: Quote, Profile, Research)(BRKb.N: Quote, Profile, Research), in its second acquisition this week, agreed to buy the NRG NV reinsurance unit of ING Group NV (ING.AS: Quote, Profile, Research)(ING.N: Quote, Profile, Research) for about 300 million euros ($441 million).

ING, the Dutch financial services company, said on Friday it is selling its Dutch reinsurance unit to an insurance unit of Berkshire so it can focus on its own insurance, banking and asset management businesses.

On Tuesday, Berkshire agreed to pay Chicago's Pritzker family $4.5 billion for 60 percent of Marmon Holdings Inc, whose products include railroad tank cars, pipes, wiring and water treatment systems. Berkshire plans to buy the rest of Marmon by 2014.

Omaha, Nebraska-based Berkshire owns more than 70 businesses. It is best known for its insurance holdings, such as the Geico Corp auto insurer as well as Buffett investments. Berkshire's main reinsurance operations include General Re Corp and the Berkshire Hathaway Reinsurance Group.

ING expects the sale to result in a 100 million euro ($147 million) aftertax loss in 2007, and an improvement of 0.47 percentage points in its debt-to-equity ratio in 2008.

ING plans to use sale proceeds to fund operations, previously announced acquisitions and a 5 billion euro share buyback program, an ING spokesman said.

The NRG transaction is subject to regulatory approval and expected to close in the first half of 2008, ING said.

(1 euro = US$1.47)

(Reporting by Gilbert Kreijger and Jonathan Stempel; Editing by Erica Billingham/Jeffrey Benkoe)