Explosives of “devastating power” were found near the Turkstream pipeline in Serbia that carries Russian natural gas to Hungary and beyond, leaders from the two countries said on Sunday.

Hungarian Prime Minister Viktor Orban said Serbian President Aleksandar Vucic told him that explosives had been found near the pipeline, which transports Russian gas through the Balkans to Central and Eastern Europe.

“Our units found an explosive of devastating power,” Vucic, a close ally of Orban, said in a post on Instagram. “I told PM Orban that we would keep him updated on the investigation.”

Orban, who held a phone call with Vucic, said in a Facebook post he had called an extraordinary defence council meeting on Sunday.

The incident comes a week before pivotal elections on April 12 in Hungary where nationalist Orban fights to hold onto his more than 16-year grip on power, with his party trailing the opposition Tisza party in polls.

Orban had in February scaled up security around energy infrastructure in the country. He has upped the stakes in the election saying that it was a choice between war or peace.

Budapest has also been in a dispute with Ukraine over a halt in oil supplies via the Druzhba pipeline. Orban’s Fidesz party has sought to associate opposition leader Peter Magyar with Brussels and Ukraine, suggesting that voting for his Tisza party means voting for tanks and war.