Japan's move to bar most used-car sales to Russia has slammed the brakes on a trade nearing $2 billion (¥299 billion) annually that had boomed in the shadow of sanctions over Ukraine elsewhere, according to trade data and market participants.

In early August, Japan's government banned exports of all but subcompact cars to Russia, cutting off a lucrative back channel in trade in used Toyotas, Hondas and Nissans for a network of brokers and smaller ports, especially Fushiki, an export hub in Toyama Prefecture on the Sea of Japan.

While wiping out Russia's biggest source of used cars, the sanctions have driven down prices for secondhand cars in Japan and left brokers scrambling to send vehicles to other regions, especially right-hand drive markets in New Zealand, Southeast Asia and Africa.