Danske Bank, which was badly affected by its exposure to Ireland, said it may not be able to pay its 2013 dividend in full after the Danish regulator said it must set aside more cash to cover risk.
Danske shares fell nearly 6% on back of the news.
Nordic regulators are among the toughest in Europe and their banks are, as a result, some of the best-capitalised.
However Denmark has been a particular trouble spot in the region due to a burst property bubble.
Danske, which has not paid a dividend for five years, suffered significant property-related losses in Ireland.
It recently dropped the name National Irish Bank and rebranded as Danske Bank here.
In a recent regional crackdown on how banks calculate risk, Sweden's regulator last month introduced a 15% floor on mortgage default risk.
Mortgage lenders had maintained single-digit floors - amongst the lowest in Europe.
Norway is considering imposing a 35% floor.
"It is still our intention to start paying a dividend for 2013 ... though perhaps not to the full amount," Chief Financial Officer Henrik Ramlau-Hansen said on a call with analysts.