JAG's move comes as City Index Eleventh flagged a second bid to buy the energy and environmental services firm and said it could boost its stake close to 33% before launching the bid.

The fund boosted its stake to at least 25.87% by last week without respecting the pledge made by the Japanese firm, JAG said.

City Index Eleventh could not be immediately reached for comment.

Murakami's fund initially began building a stake in JAG after Carlyle Group teamed up with JAG chairman and CEO Tetsuo Yamashita on a management buyout in November.

It launched a counter bid to block Carlyle's bid but withdrew it after JAG announced a large special dividend payout.

(Reporting by Junko Fujita; Editing by Emelia Sithole-Matarise)