TOKYO, June 28 (Reuters) - Japanese government bond yields eased back from recent highs on Friday but remained on course for a substantial weekly advance as the embattled yen fuelled bets for near-term policy tightening by the Bank of Japan.

The 30-year JGB yield retreated 1 basis point (bp) to 2.265% as of 0452 GMT, after reaching a 14-year peak of 2.29% on Thursday. That puts it 12 bps higher for the week.

The 20-year yield eased 1.5 bps to 1.890%, down from a nearly 13-year top of 1.93% hit in the previous session. It is up 9.5 bps since last Friday.

The 10-year JGB yield fell 1 bp to 1.06%, after reaching 1.08% on Thursday, the highest level this month. For the week, it is up 9 bps.

Longer-end yields lost some ground on Friday with the BOJ's regular bond purchase operations - known locally as rinban - that day focused mainly on longer-dated tenors. Bond yields fall when prices rise.

However, the trend remained for higher yields as expectations build for an additional interest-rate hike at the BOJ's July meeting, with the central bank under pressure to support the yen after it slid to a 38-year trough of 161.27 per dollar on Friday.

"The yen effect is having an impact," said Shoki Omori, chief Japan desk strategist at Mizuho Securities.

"Rinban is distorting things to a certain extent today, but the point is the yen going cheaper," he said. "People are trying to sell bonds because rate expectations towards the July meeting are going higher, period. Very simple."

The two-year JGB yield eased 1 bp to 0.36%, but remained on course for a 5.5 bps rise this week.

The five-year yield lost 0.5 bp to 0.59%, also set for a 5.5 bps weekly advance.

Benchmark 10-year JGB futures rose 0.06 yen to 142.74, but were off 0.90 yen over the course of the week. (Reporting by Kevin Buckland; Editing by Janane Venkatraman )