A check on public joint-stock company Ukrtransnafta has revealed the replacement of Urals oil removed from pipelines and stored at Kremenchuk oil refinery with Ukrainian-made oil, a source in national joint-stock company Naftogaz Ukrainy has told Interfax-Ukraine.

"We’ve conducted a stocktaking of pipeline oil at Kremenchuk oil refinery with taking oil for tests. After conducting analysis [for sulfur content] it was established that Urals oil [sulfur from 1.5% and higher] is not stored at all and it was replaced by Ukrainian-made oil [better in quality]," he said.

The source said that the stocktaking was conducted on June 30, 2015 with the participation of Head of Kremenchuk branch of Ukrtransnafta Vitaliy Velychko and his deputy Halyna Petrova.

He said that Velychko and Petrova previously worked in private firms in subordination to the current member of the supervisory board of Ukrnafta Petro Stoliar.

"His beating [Stoliar's] could be linked not only with Ukrnafta, but with actions of new managers of Ukrtransnafta," the source said.

Ukrtatnafta has denied the allegations.

"Initially the information was presented in one-sided manner, in a corrupt form, with the application of not the full package of documents and without experts' conclusions. We pay attention to the fact that the information was deliberately presented in this way to change the comprehensive picture, presenting false and naked conclusions. The conclusions are not true and they are not professional," Ukrtatnafta said in a press release.

As reported, in summer 2014, a total of 628,400 tonnes of oil was pumped out of the Ukrtransnafta's pipelines. Some 232,600 tonnes is stored in the reservoirs of Ukrtransnafta, 239,900 tonnes in public joint stock company Ukrtatnafta's reservoirs, 101,900 tonnes in Naftokhimik Prykarpattia's reservoirs and 46,700 tonnes in Halychyna oil refinery's reservoirs.