* Topix rebounds after hitting 28-yr low on Monday
* Canon rises on share buyback plan; Sony regains 1,000 mark
* Fast Retailing sinks after weak Uniqlo same-store sales
* Olympus up on report of capital raising via share placement
TOKYO, June 5 (Reuters) - Japan's Nikkei share average on Tuesday edged away from the previous session's hefty losses, with investors trimming bearish bets ahead of emergency talks by the Group of Seven leading industrialized powers on the euro zone crisis.
The Nikkei added 0.6 percent to 8,343.49, helped as Canon Inc rose 3.6 percent after it said it plans to buy back up to $640 million worth of its own shares. The camera and printer maker was the top-weighted gainer and the most heavily traded stock on the main board by turnover.
But Fast Retailing Co Ltd lost 5.5 percent after reporting May same-store sales at its Uniqlo shops had dropped by around 10 percent.
The broader Topix index gained 1 percent to 702.66, regaining the 700-mark after hitting its lowest in more than 28 years on Monday.
Naomi Fink, Jefferies' Japan equity strategist, said she remained long volatility and short securities and banks.
"There are still quite a lot of event risks, so I am not getting out of that vol position anytime soon ... Today there is a short-covering rally going on," Fink said.
"Factory orders were not as good as expected from the U.S. People are wondering whether policies in China are going to be conducive for revitalisation. I don't see that optimism coming out just yet."
The emergency talks by the G7 finance chiefs on Tuesday come as alarm is intensifying over strains in the 17-nation European currency area.
Sony Corp advanced 1.7 percent to above 1,000 yen, after falling below that level to its lowest close in 32 years on Monday.
Scandal-hit Olympus Corp climbed 3.8 percent after the Sankei newspaper reported that it is considering raising about 50 billion yen ($640 million) through a third-party share allotment.
The benchmark Nikkei has shed 18.6 percent since hitting a one-year peak on March 27 on concerns over the deepening euro zone debt crisis and slowing growth in the United States and China.
Despite Tuesday's gains, the Nikkei was still deep in "oversold" territory, with its 14-day relative strength index at 26.9. Thirty or below is deemed oversold. ($1 = 78.2800 Japanese yen) (Reporting by Dominic Lau; Editing by Joseph Radford)