Energean has begun pumping gas to its floating production facility in the offshore Karish gas field as part of reverse flow testing procedures approved by the Israeli government, the London-listed energy group said on Sunday.
It said the testing phase is an important step in the commissioning process of the so-called FPSO Energean Power facility.
The development of the Karish field, about 80 km (50 miles) west of the Israeli city of Haifa, has raised tensions between Israel and Lebanon in their protracted dispute over maritime boundaries, drawing threats of war from the Iran-backed Hezbollah movement.
The United States has been mediating indirect talks on the issue since 2020.
Last week Israel rejected revisions to a draft agreement on demarcation of the two countries' maritime borders at a critical phase of negotiations.
Energean has said its floating production storage and offloading vessel is due to start production at Karish in the third quarter. On Saturday Israeli Defense Minister Benny Gantz said Israel was "nearing production" at the site.
(Reuters - Reporting by James MackenzieEditing by David Goodman)