The dispute between Belarus officials and Russian oil company Transneft has escalated to the point of the former blocking Russian oil to neighboring countries, the BBC has reported.

A fresh argument recently erupted between neighbors Russia and Belarus after the latter suddenly imposed a new custom tax on Russian oil piped through its territory.

Transneft, the company that owns the piped oil, argued that cross border accords between the two former Soviet nations stipulated that such a unilateral action could not be taken and therefore the new tax was unlawful.

Transneft’s refusal to pay the tax has resulted in Belarus instigating legal proceedings against the Russian firm. However, the dispute, which follows closely behind the acrimonious agreement by Belarus to dramatically increase the price it pays for imports of Russian gas, has now escalated further, to the point where Belarus has started to block the onward supply of oil to recipient countries.

According to the BBC, Poland has reported that all Russian oil supplies sourced through Belarus have ceased. Meanwhile, Ukraine and Germany have also seen their supplies stopped.

The BBC reports that Polish officials have asked Belarus for an explanation for the development, with the eastern European country responding that inquiries should be directed to Transneft.