Ukrainian opposition leader Dmitry Yarosh said Sunday he'd destroy the Soviet-era gas transmission network through Ukraine in response to Russian "occupiers," Russian news agency RT reported.
European consumers get about a quarter of their natural gas from Russia, though the bulk of that heads through Ukraine's pipeline system.
The Ukrainian Interior Ministry said Monday it was taking the necessary security precautions.
"The National Guard and Security Service of Ukraine have put in place special protective measures concerning the gas transmission and distribution system of Ukraine," a statement carried by Russian news agency RIA Novosti said. "This decision was made to ensure the safety and smooth operation of critical infrastructure in the country."
Conflict erupted in Ukraine in November when ousted President Viktor Yanukovych, a Kremlin ally, decided to suspend efforts to sign free trade and association agreements with the European Union.
Authorities in Crimea, a Ukrainian peninsula which voted Sunday to join Russia, alleged Ukrainian forces were trying to starve the territory of natural gas, which provides a source of income.