Russia says oil flows to three European countries have been halted.

In another sign of the fragility of Europe’s dependence on Russian energy, the state-owned pipeline operator said Tuesday that oil had stopped flowing through the southern branch of the main link to Eastern Europe.

Transneft, which controls Russia’s stretch of the pipeline, said its July payment to the Ukrainian operator of the artery, Ukrtransnafta, had been returned. Transneft blamed issues related to European sanctions aimed at punishing Russia for its invasion of Ukraine.

In response, Ukraine halted oil deliveries to Hungary, Slovakia and the Czech Republic through the pipeline, according to Transneft. The three countries have been exempted from a European Union decision to ban imports of Russian oil starting later this year.

Ukrtransnafta had no immediate comment.

Hungary, Slovakia and the Czech Republic sit on the southern end of the Cold War-era pipeline — called Druzhba, the Russian word for friendship. All three rely heavily on Russia to meet their energy needs and had lobbied their European partners to exempt oil delivered by pipeline from a ban on Russian imports passed by Brussels in late May.

Germany, which sits at the northern end of the pipeline and has also continued to receive oil from Russia, was not affected by the interruption, Transneft said.

Since invading Ukraine in February, President Vladimir V. Putin of Russia has shown that he is willing to use his control of the energy spigot as leverage over Europe. He has also demonstrated his knack for keeping his adversaries off-balance by sending mixed signals and trying to play Western allies against one another.

In the spring, Russia cut deliveries of natural gas to several European countries, starting with Bulgaria and Poland, then adding Finland. In June, on the day that the leaders of France, Germany and Italy visited Kyiv, those countries reported a shortfall of deliveries of Russian gas, as did Austria and the Czech Republic.

Flows through the Nord Stream 1 pipeline to Germany, Europe’s main consumer of Russian gas, have been slashed by 60 percent and then by 80 percent. Moscow blamed the disruption on a pipeline component that was being refurbished by a German company at a factory in Canada, causing tensions between Ottawa and Berlin.