THE city of Berlin started switching off spotlights illuminating its historic monuments as part of a national effort to save energy in the face of Russian gas shortages.

Some 200 buildings and landmarks including Berlin's red-brick city hall, State Opera House and Charlottenburg Palace will fall in darkness at night, officials in the German capital said this week.

"Given the war against Ukraine and the energy policy threats by Russia, it's important that we be as careful as possible with our energy," the city's chief official for the environment, Bettina Jarasch, said.

Jarasch of the Green party said that included consumers and industry but also public institutions, calling the darkened monuments "the right thing to do to make a visible contribution".

The policy at first affected six monuments from Wednesday night and will eventually encompass 200 buildings and landmarks and their 1,400 spotlights over the next four weeks, Jarasch's office said.

An electrical services firm will shut off 100-120 lights per day without dismantling them, keeping the policy temporary.

Thus the cash-strapped capital will not save money as the labour costs are expected to match the benefit of cutting energy use.

President Frank-Walter Steinmeier said this week he wanted to set an example by keeping his official residence, Bellevue Palace in Berlin's sprawling Tiergarten park, dark at night.

Several German cities have said they would step up efforts to trim the use of power and gas.

The centre-left-led government of Chancellor Olaf Scholz has called for weeks for a national effort to save energy amid soaring prices due to the Russian invasion of Ukraine.

German officials have also warned that the Kremlin could cut off supplies this winter in retaliation for biting Western sanctions against Moscow over the war.

The energy-savings efforts include reducing the use of air conditioning, encouraging use of public transport and pushing the use of more efficient shower heads.

Before the Ukraine war, Germany bought 55 percent of its natural gas from Russia.

Although the rate had fallen to 35 percent by early June, Europe's top economy is still heavily dependent on Russia for its energy, which it says Moscow is using as a "weapon".

On Wednesday, Russian state-run energy giant Gazprom slashed deliveries of gas through the Nord Stream pipeline to Germany to 20 percent of capacity from the previous 40 percent.