Western nations have rejected the Russian demand for ruble payments, arguing it would undermine the sanctions imposed against Moscow over the war in Ukraine.

``There have been several comments from the Russian side that if this (payments in rubles) doesn't happen, then the supplies will be stopped,'' Economy Minister Robert Habeck said. ``In order to be prepared for this situation I have today triggered the early warning level.''

Habeck, who is also Germany's energy minister and vice chancellor, told reporters that this was the first of three warning levels and entailed the establishment of a crisis team in his ministry that will step up monitoring of the gas supply situation.

The measure was a precautionary one and Germany's gas storages are currently filled to about 25% capacity, he said.