Iran said on Saturday that hackers had briefly attacked its data centres and left an image of the American flag on their network with a warning: “Don’t mess with our elections”. The attack was neutralised soon and no data was lost, said Hadi Sajadi, the deputy head of the Information Technology Organisation of Iran.

Information Technology Minister Mohammad Javad Azari-Jahromi claimed that the cyber attack had brought down networks globally, including in India, the United States and China. Iran’s share of the number of affected devices was 2%, he told state media, according to Reuters.

Some Indian government websites were down on Friday evening and Chinese characters appeared briefly on the defence ministry’s website. India, however, denied reports that they were hacked and claimed it was because of a hardware problem.

“The attack apparently affected 2,00,000 router switches across the world, including 3,500 in our country,” the Iranian government said on Saturday. The attack hit internet service providers and cut off web access for users, the statement said, blaming a vulnerability in routers from Cisco.

Azari-Jahromi said it was not yet clear who had carried out the cyber attack.