"The share of Russian oil imports via the Druzhba pipeline versus imports from other countries via the IKL pipeline reached about 65/35 percent in the first half," Barbora Putzova, spokeswoman for the state-owned Mero company, told AFP.

In 2022, the share was 56 versus 44 percent in favour of Druzhba, she added.

Industry and trade ministry data have shown this year's share of oil transported by Druzhba into the EU member state was the highest since at least 2016.

The EU slapped a ban on most oil imports from Russia in May 2022, three months after Russia invaded Ukraine, but the Druzhba pipeline was exempted.

Jiri Gavor, head of the Czech Association of Independent Energy Suppliers, said Poland's PKN Orlen, which runs Czech refineries, was probably driven by economic reasons to stick to Russian oil.

"I'd say PKN Orlen... benefits from the fact that oil transit via Druzhba is not banned here so far, it's legal and it's cheaper than oil from other sources," he told AFP.

In May, Mero said it had signed a deal to end Czech dependence on Russian oil as it pledged to finance an expansion of the Transalpine oil pipeline (TAL) which supplies oil from Italy to central Europe.

TAL transports oil from the Italian port of Trieste to southern Germany, where it connects to the IKL pipeline taking it to the Czech Republic.

The country's TAL capacity is set to double to an annual eight million tonnes of oil starting in 2025.

Prague already weaned itself off Russian gas earlier this year.