Germany's finance and foreign ministers cautioned Sunday against banning Russian energy imports as the West searches for ways to tighten the screws on Moscow over its invasion of Ukraine.

With his country fighting for its existence two weeks since the incursion, Ukrainian leader Volodymyr Zelensky has urged his Western allies to levy additional sanctions against Moscow, including boycotting its lucrative oil and gas sector.  

Earlier Sunday, chief US diplomat Antony Blinken said the United States and Europe were "very actively discussing" targeting Russian fossil fuels as the war intensifies.

But in Germany, which currently holds the rotating presidency of the G7, foreign minister Annalena Baerbock said such a move would be pointless since it could not be sustained long term.

"It's no use if in three weeks we find out that we only have a few days of electricity left in Germany and therefore we have to go back on these sanctions," she told a German public broadcaster.

In a separate interview, she added that Germany was prepared "to pay a very, very high economic price" but "if tomorrow in Germany or Europe the lights go out, it's not going to stop the tanks".

Germany is dependent on Russian fossil fuels, importing an estimated 55 percent of its gas and 42 percent of its oil and coal from Russia.

German Finance Minister Christian Lindner was also sceptical of an oil ban.

"We should not limit our ability to sustain ourselves," he told the newspaper Bild.

European and British gas prices surged to record peaks last week on supply disruption fears. And oil prices have continued to skyrocket, with Brent futures leaping to almost $140 a barrel, the highest since 2008.

Instead of boycotting Russian energy, the next round of G7 sanctions against should hit oligarchs who have gotten rich under President Vladimir Putin, the finance minister suggested.

"Those who have profited from Putin and stolen the wealth of the Russian people, also through corruption, cannot enjoy their prosperity in our western democracies," Lindner told ARD television.

On Thursday, the United States and the United Kingdom added more Russian oligarchs to a blacklist of businessmen associated with the Kremlin already targeted by the European Union.

The same day, France said it had seized a superyacht owned by Russia's oil czar Igor Sechin on the French Riviera.

Russia is already dealing with a wave of sanctions designed to isolate it from the international financial system.

Putin has likened the global blacklisting to a declaration of war.