JGBs rise on ongoing concerns about Europe debt

* Yield curve steepens as superlong tenor lags

* 10-, 30-yr yield spread at widest since Oct 2010

* 10-yr futures shrug off stock rise, end at session high

TOKYO, June 27 (Reuters) - Japanese government bonds rose on Wednesday, getting a safe-haven lift in the waning days of the April-June quarter from ongoing fears about Europe's debt woes ahead of a meeting of regional leaders.

Investors remained sceptical that a two-day summit of European Union leaders beginning on Thursday would result in any solid progress towards resolving the region's debt crisis.

JGB investors have only a few days left to make quarter-end adjustments to their portfolios.

Some strategists expect the superlong tenor to benefit from month-end buying by pension funds to extend the duration of their portfolios, but others expect them to hold off and wait for better yield levels.

"We're still waiting to see if the unexpected happens at the EU side," said Shogo Fujita, chief Japan bond strategist at Bank of America Merrill Lynch.

"Pension funds have plenty of money to put to work, but I'm not too sure you'll see much happen on the domestic side because it is June-end, and you'd expect more in September-end because that's the semiannual year-end," he added.

Investors also kept an eye on domestic politics, although Tuesday's passage of a tax-hike bill in parliament's lower house had no immediate market impact.

Japanese Prime Minister Yoshihiko Noda faces a split in his party that could trigger a snap election.

Japan's Nikkei average broke a three-session losing streak as investors snapped up construction and real estate shares on expectations that they would benefit from a surge in housing demand ahead of the sales tax increase in 2014. But the stock market rally had a negligible impact on the JGB market.

"JGB futures extended gains even as stocks rose, showing no correlation today. Volume is thin ahead of the quarter-end," said a fixed-income fund manager at a Japanese asset management firm.

The 10-year JGB futures contract for September ended up 0.10 point at its session high of 143.90. Volume of 17,324 contracts was higher than the previous two sessions, in which activity fell to its lowest levels since January, but was still far below a three-month high of 65,816 contracts on June 5.

In late afternoon cash bond trading, the 10-year JGB yield slipped 1.5 basis points to 0.805 percent, inching back towards a nine-year low of 0.790 percent hit on June 4.

The yield curve steepened as the superlong sector slightly lagged, with the 20-year yield losing 1 basis point to 1.650 percent and the 30-year yield shedding half a basis point to 1.875 percent.

The yield spread between 10-year and 30-year bonds widened to 1.070 points, its widest since October 2010.

The five-year yield was flat at 0.210 percent.