TOKYO - Japan's biggest oil refiner Eneos Holdings said on Thursday it had raised its stake in Vietnam National Petroleum Group (Petrolimex) to 9% from 8% earlier, as the companies plan to expand the scope of their potential ties into liquefied natural gas (LNG) and clean energy.

Eneos, which was formerly known as JXTG Holdings, bought an 8% stake in Petrolimex in 2016 and originally sought to jointly build a refinery in Vietnam, followed by a feasibility study on the cooperative project using Eneos' Marifu refinery in Japan.

But the talks did not result in any concrete joint projects.

Eneos has boosted its stake to accelerate their talks and the two companies now plan to consider potential collaborations in wider areas, including refinery operation, LNG terminal and power plant operations, renewable energy and hydrogen business, an Eneos spokeswoman said.

She declined to comment on which project will likely to start first and when, as well as on why the talks have failed so far to create an actual joint project.

(Reporting by Yuka Obayashi; Editing by Rashmi Aich) ((Yuka.Obayashi@thomsonreuters.com; +813-4563-2761;))