Japan in early July unveiled tough restrictions on exports crucial to tech titans such as Samsung, following a series of South Korean court rulings ordering Japanese firms to pay for forced labour during World War II.

The two countries on Friday removed each other from their "white lists" of trusted trading partners, despite US calls for both to calm tensions.

Even before Friday's decision, angry South Koreans had been making their fury known, shunning Japanese brands in favour of local ones, for items such as beer, clothing, cosmetics and even pens.

Data on Monday showed that Koreans turned away from Japanese vehicles last month.

Honda saw its July sales in the South slump 33.5 percent year-on-year, while Toyota Motor's sales tumbled 32 percent, according to data from the Korea Automobile Importers and Distributors Association (KAIDA).

Honda told AFP that it was watching the situation "closely" and "with caution".

An executive at Toyota Korea said that it was "difficult for us to say that the current Japan-South Korea trade row is the only reason why this has happened".

"There are a lot of factors that affect our sales," she added.

Lexus saw sales down 24.6 percent from the previous month, although its year-on-year sales were up 32.5 percent.

As the trade row escalated local media have reported cases of Japanese cars being vandalised and covered in kimchi, the fermented cabbage that is a mainstay of the Korean diet.

Last month, some 50,000 members of a South Korean grocery store owner association said they had stopped orders of some or all Japanese products.