UPDATE 2-Norske Skog CEO resigns, to head Statkraft

* Rynning-Tonnesen to become CEO of Statkraft June 1, 2010

* Says key challenges remain, new job 'unique opportunity'

* Norske Skog shares fall 2 pct

* Statkraft to implement measures to adapt to weaker market

(Adds share price, Statkraft Q3 results)

By Richard Solem

OSLO, Nov 12 (Reuters) - Norwegian paper producer Norske Skog (NSG.OL) said on Thursday Chief Executive Christian Rynning-Tonnesen would leave the company to head state-owned power company Statkraft [STATK.UL] from June, 2010.

"He has made an outstanding effort as CEO in what has been a very demanding period for the group," Chairman Eivind Reiten said, adding the board would begin the process of recruiting his successor shortly.

The global financial crisis has compounded years of difficulties at Norske Skog and the rest of the paper industry, which is struggling with weak demand and overproduction.