Kazakh oil exports from the Black Sea suspended

This effectively blocks exports from Kazakhstan, handled mainly by a consortium partly owned by American energy companies.

The lack of port access for foreign ships, which has also affected Russian oil exports from the port of Novorossiysk, could affect more than 2% of global oil supply , Reuters calculated based on data on loadings in the region.

This comes days after the EU imposed new sanctions on Russia and complicated the activities of the Caspian Pipeline Consortium (CPC), whose shareholders include Chevron and ExxonMobil, Reuters wrote.

CPC ships the oil through a pipeline that carries more than 80 percent of Kazakhstan's total oil exports, and then through the Russian Yuzhnaya Ozereyevka terminal.

On Monday, President Vladimir Putin signed a law under which foreign ships will have to obtain permission from the Russian FSB security service to access the country's ports , Reuters recalled.

The new regulations came into force immediately after the decree was published.