UPDATE 1-Nordea replaces CFO in surprise management change

(Adds quotes, details)

* CFO, who is leaving, says decision was surprise

* Head of group operations taking over immediately

STOCKHOLM, Jan 16 (Reuters) - Nordea is to replace its chief financial officer in an unexpected management reshuffle at the Nordic region's biggest bank.

Chief Executive Christian Clausen said in a statement that Torsten Hagen Jorgensen, who was head of group operations and like Clausen is also Danish, would take over immediately from current CFO Fredrik Rystedt, who will leave the bank.

"Fredrik has been a competent and highly professional CFO and contributed substantially in managing Nordea through the European financial crisis," Clausen said in a statement.

Rystedt said he had found out about the change on Monday.

"Christian wanted to change the leadership team and of course it is the CEO's prerogative to choose the people to work with," he told Reuters. "I must admit, it was a big surprise ... I really liked the company and enjoyed my job a lot."

One analyst said the decision came out of the blue and that Jorgensen, who has been with the bank since 2005, was a relative unknown.

Rystedt took over as CFO at Nordea the start of the global financial crisis in 2008 when he left as CFO of Electrolux , the world's second-biggest appliances maker.

Nordic banks have been shielded from the euro zone's debt crisis thanks to strong capital reserves and a relatively robust Swedish economy. Nordea, though, has struggled with some exposures to the global shipping sector and a weak Danish economy.

It has built up capital since the 2008 crisis but still has the lowest capital ratio of any of its Nordic peers, a factor which analysts say has weighed on its share price.

Nordea shares closed down 0.08 percent on Wednesday compared with a 0.28 percent rise in the Stockholm blue-chip index .

Sweden, whose banking sector is about four times as big as national output due to major overseas operations in areas such as the Baltics, has already introduced tougher capital requirements for its banks than elsewhere in Europe. (Reporting by Mia Shanley, Oskar von Bahr and Sven Nordenstam. Editing by Jane Merriman)