Klaus Mueller said much had been achieved in a short time last year to diversify supply and reduce Germany's dependence on Russian gas after Moscow's invasion of Ukraine.

"When it comes to storage (tank) filling, we are now at a different level to last year ... But the biggest factor remains the weather," said Mueller. "The energy crisis is not over yet."

If Europe experienced a cold winter, Germany would benefit from any precautions taken to save energy. He urged consumers to adapt their homes to save energy by installing insulation or more efficient heating systems.

"If everything goes well, we will have full storage facilities in the late summer," Mueller was quoted as saying.

(Reporting by Madeline Chambers in Berlin; Editing by Matthew Lewis)