By Joshua Hunt

TOKYO, May 26 (Reuters) - Japanese stocks inched higher in choppy trade on Thursday following a rise in oil prices and gains on Wall Street, but indexes remained vulnerable to yen volatility as the currency see-saws against the dollar.

The Nikkei share average ended the morning session 0.3 percent higher at 16,805.63 points, paring some of its early gains due to a strengthening yen.

"Since the beginning of the month we've seen the yen slide back against the dollar but the return is far from linear and the intra-day appreciation we're seeing is enough to keep investors on their toes," said Martin King, managing partner at Tyton Capital Advisors in Tokyo.

"At present the focus is on Japan's role as host of the G7 summit and pending any egregious missteps there we expect to see a lull in volatility as the market awaits further catalysts."

Concerns about the health of the global economy and Europe's refugee crisis are among the top issues to be discussed at the G7 leaders' summit in Japan over the next two days.

Although full agreement on macro-economic policy looks hard to come by, the G7 leaders are expected to promote monetary, fiscal and structural policies to spur growth in their communique when the summit ends on Friday, government sources told Reuters.

The yen's recent weakness was still significant enough to help lift the share price of exporters like Toyota Motor Corp , which gained 0.8 percent, and Bridgestone Corp , which edged up 0.3 percent.

Shares of Mitsubishi Motors Corp soared 5.9 percent after the automaker restated its financial results for the past year to reflect a special loss of 19.1 billion yen ($174.29 million) related to controversy over its manipulation of fuel economy data.

Net profit fell only 39 percent in the year that ended in March, the automaker said, suggesting that the impact of the scandal could be limited to this year's results.

Central Japan Railway Co shares climbed 3.2 percent after the Nikkei business daily reported its high-speed Tokyo to Osaka maglev train may beat its scheduled 2045 launch by as much as eight years.

Shares of companies linked to the construction of the maglev train also rose following the report.

Drilling contractor and equipment maker Koken Boring Machine Co Ltd rose 2.5 percent while construction company Zenitaka Corp, which will take part in the building of a tunnel for the train, ended the morning session 6.2 percent higher.

The broader Topix rose 0.3 percent to 1,346.67 and the JPX-Nikkei Index 400 gained 0.3 percent to end the morning session at 12,157.27.

($1 = 109.5900 yen) (Reporting by Joshua Hunt; Editing by Kim Coghill)