Around 600 Japanese companies, including electronics major Hitachi and automaker Nissan, have reportedly been affected by last week's global cyber attack, officials confirmed on Monday.
According to the Japan Computer Emergency Response Team Coordination Centre, around 2,000 computers across 600 different companies were hit by the ransomware named "WannaCry".
Hitachi told EFE news that its email service was affected, and that some of its employees were still facing problems in accessing attachments, as well as sending and receiving messages.
Nissan Motor too, in a statement, said some of its plants were targeted by the malicious software, although business was not adversely affected.
The City Council of Osaka is still monitoring its website that crashed at 10 am on Monday.
Meanwhile, the country's Financial Services Agency has urged all domestic financial institutions, including banks, insurance and securities companies, to check if they have been affected.
The ransomware WannaCry, which asks users for a payment in the Bitcoin digital currency in order to regain access to computers, affected computer systems in at least 150 countries, including the National Health Service in the UK, large companies in France and Spain, the largest rail network in Germany, government offices in Russia and universities in China and Taiwan.