* BOJ say no more monetary easing; potential disappointment * Nikkei rises but sentiment unsteady ahead of election * DeNA soars on share buyback By Sophie Knight TOKYO, June 15 (Reuters) - Japan's Nikkei share average firmed during Friday's morning session, but gains on a report that central banks will take action to prevent a credit squeeze if turmoil hits the markets was limited by bearish sentiment ahead of the pivotal Greek election. Investors cut their exposure to Europe and focused on stocks driven by domestic demand such as Fast Retailing, convenience store operator Lawson and pharmaceuticals. " Sellers are short-covering while net buyers are cutting down a little bit for protection, but the market is very illiquid," said Hideyuki Ishiguro, assistant manager of investment strategy at Okasan Securities. "But the election result will at least give the market a direction. Even in the worst-case scenario a policy response should come forth to calm the markets." The Nikkei rose 0.3 percent to 8,595.88 while the broader Topix also gained 0.3 percent to 727.88 after both indexes entered negative territory in early trading. DeNa co Inc was the top gainer, shooting up 14 percent as the second most-traded stock by turnover after the social gaming site operator said on Thursday it will buy back up to 10 percent of its outstanding shares - 20 billion yen worth.