Russian fuel exports are showing signs of a slowdown just five days after the European Union — Moscow’s main market — banned seaborne shipments of its refined oil products. 

Flows of petroleum products ranging from diesel to jet fuel are set to tumble to about 1.9 million barrels a day in the week after the sanctions took effect, according to data from Vortexa Ltd. compiled by Bloomberg. That’s about 37% below average levels during the previous four weeks.

To be sure, the data are somewhat noisy, since the ban has only been in place since Feb. 5. Russia’s global crude flows also slumped — and then rebounded — after the EU prohibited crude imports from the country in December. 

Russia this month was planning to export the most diesel from its key western ports in at least three years. However, the bulk of the decline in shipments observed so far has been in diesel and gasoil. 

About 2.7 million barrels of the fuel has been loaded since the ban took effect. Most of those cargoes are in transit, heading toward the Mediterranean Sea and Latin America. Flows were more than 5 million barrels during the same period in January.

Shipments of other refined products, including fuel oil and naphtha, have also slipped on average in recent days. 

Russia announced on Friday that it would cut oil production in March, in retaliation for Group of Seven price curbs on its sales. Were Russia to struggle to export fuels for a sustained period, its refineries might be forced to curb processing, limiting their own crude purchases.