Fearing Russia might cut off natural gas supplies, the head of Germany's regulatory agency for energy called on residents Saturday to save energy and to prepare for winter, when use increases.

Rs Federal Network Agency President Klaus Mueller urged house and apartment owners to have their gas boilers and radiators checked and adjusted to maximise their efficiency.

"Maintenance can reduce gas consumption by 10% to 15% ," he told Funke Mediengruppe, a German newspaper and magazine publisher.

Mueller said residents and property owners need to use the 12 weeks before cold weather sets in to get ready.

He said families should start talking now about "whether every room needs to be set at its usual temperature in the winter -- or whether some rooms can be a little colder."

The appeal came after Russia reduced gas flows to Germany, Italy, Austria, the Czech Republic and Slovakia earlier this month, as European Union countries scramble to refill storage facilities with the fuel used to generate electricity, power industry and heat homes in the winter.

Russian state-owned energy company Gazprom blamed a technical problem for the reduction in natural gas flowing through Nord Stream 1, a pipeline which runs under the Baltic Sea from Russia to Germany.

The company said equipment getting refurbished in Canada was stuck there because of Western sanctions over Russia's invasion of Ukraine.

German leaders have rejected that explanation and called the reductions a political move in reaction to the European Union's sanctions against Russia after it invaded Ukraine.

Vice Chancellor Robert Habeck, who is also Germany's economy and climate minister and responsible for energy, has warned a "blockade" of the pipeline is possible starting July 11, when regular maintenance work is due to start.

In previous summers, the work has entailed shutting Nord Stream 1 for about 10 days, he said.

The question is whether the upcoming regular maintenance of the Nord Stream 1 gas pipeline will turn into "a longer-lasting political maintenance," the energy regulator's Mueller said.