The financial details of the deal, which has been approved by German regulators, were not disclosed.

The contracts will supply 6 billion kWh, or about 614 million cubic metres (mcm), of gas to 100 industrial customers until 2022, Axpo said.

Axpo, wholly owned by cantons or regions in northeast Switzerland, has been active in Germany since 2003 and already supplies gas on the wholesale market to municipal utilities and industrial companies.

Naturgy's contracts add to Axpo's 2017-2018 total of 2.9 billion kWh in gas sales, latest data available on its website show.

The Swiss group is also active in renewable energy such as wind and solar projects.

Naturgy is one of Spain's largest energy companies with 38.7 billion cubic metres (bcm) of gas sales around the world, its annual report showed.

Naturgy and Axpo did not immediately respond to emailed questions.

(Reporting by Sabina Zawadzki; editing by Jason Neely)