President Vladimir Putin on Tuesday condemned measures taken against Russian gas giant Gazprom in Europe over the conflict in Ukraine and warned of potential reprisals.
"The situation in the energy sector is worsening as a result of non-market, brute measures, including administrative pressure on our company Gazprom in some European countries," Putin told officials in a televised meeting, after Germany said on Monday it was temporarily taking control of Gazprom's German subsidiary.
"We are already hearing statements from officials about the possible nationalization of our assets," Putin said.
"If we go that far, let's not forget that this is a double-edged sword."
Berlin said its move to take over Gazprom Germania until Sept. 30 was aimed at securing energy supply and critical infrastructure, amid growing distrust between Russia and the West.
EU antitrust investigators raided the German offices of Gazprom last week, on suspicion the Russian company had illegally pushed up prices in Europe.
Ukraine has repeatedly urged European nations to stop imports of Russian gas over the conflict.
Russia provides roughly 40% of the EU's gas supply, mainly to Germany, Italy and a few eastern European countries.