By Maarten van Tartwijk 

AMSTERDAM--Dutch bank ING Groep NV Thursday said it will move ahead with plans to float its NN Group insurance business in what is likely to be one of Europe's biggest initial public offerings this year.

ING said it would float a minority stake in NN on the Amsterdam stock exchange in the coming weeks, if market conditions stay favorable. ING Chief Executive Ralph Hamers said the sale could happen at "any moment" and that the stake will be "sizable." Analysts value NN at between EUR6 billion and EUR8 billion ($8.2 billion-$10.9 billion).

The NN IPO marks the final and most significant step in an overhaul imposed by the European Commission following a government bailout in 2008. ING was ordered to sell its global insurance business and has to sell at least 50% of NN before the end of 2015. ING has already disposed of insurance assets in the U.S., Latin America and Asia.

Europe's IPO market has gathered steam in recent months, with a series of share sales currently under way. The U.K.'s Lloyds Banking Group PLC said it plans to float its TSB retail banking unit on the London Stock Exchange later in June.

To woo investors, ING said NN will pay a dividend of EUR175 million over the second half of 2014 and that it will target a payout policy of 40% to 50% of its operating result from 2015. In addition, excess capital could also be returned to shareholders, it said.

NN, which employs about 12,000 people, includes life insurance and asset-management operations. It generates most of its income in the Netherlands but also has a presence in more than a dozen other countries, including Belgium, Poland and Japan.

Analysts have questioned NN's growth prospects, as it struggles with a difficult home market and a large closed book of variable annuities in Japan. NN last year reported a pretax loss of EUR52 million.

NN is also dogged by lawsuits from clients in the Netherlands who claim they were charged excessive fees on certain unit-linked insurance plans. The company in 2009 agreed to pay out hundreds of millions of euros in compensation, but has warned that a flood of new lawsuits may result in additional costs.

"We still have a number of clients that are not happy with the products we have sold," said Lard Friese, NN's CEO Thursday. "It isn't possible to give a reliable estimate on the financial consequences."

Write to Maarten van Tartwijk at maarten.vantartwijk@wsj.com