* Olympus shares continue plunge after CEO firing
* Nikkei remains solidly above 25-day moving average
By Lisa Twaronite
TOKYO, Oct 17 (Reuters) - The Nikkei stock average rose to a six-week high on Monday, tracking U.S. gains on earnings hopes and on expectations that Europe will come up with a plan to contain its debt crisis.
Shares of Olympus plunged 22 percent, extending deep losses on Friday after the company's British former chief executive said in a Financial Times interview he was fired for probing payments relating to acquisitions made by the company before he joined the board.
The Nikkei added 1.5 percent to 8,881.42 after earlier rising as high as 8,911.70 shortly after the open. It was the first time for the benchmark to trade above the 8,900 level since Sept. 2, and it remains solidly above its 25-day moving average of 8,649.
The gains follow a 1.7 percent climb for last week.
The broader Topix index gained 1.6 percent to 761.02.
"The shocking developments at Olympus do not seem to be affecting broader market sentiment, as investors cautiously buy back other Japanese shares as European worries fade," said Fujio Ando, senior managing director at Chibagin Asset Management.
Some analysts said Japanese shares will move within a range until more U.S. corporate results are out. This week's U.S. results include those from Goldman Sachs , Bank of America , Apple Inc .
Investors will also continue to watch developments in Europe this week. The world's leading economies at a G20 meeting pressed Europe to act decisively within eight days to resolve the crisis, raising hopes that officials will agree on the outlines of a plan in time for a European Union summit on Oct. 23.
Olympus was down 22.3 percent at 1,589 yen with volume jumping to more than 10 times the company's 30-day average.
(Editing by Edwina Gibbs)