The European Union placed on Monday OpenAI's ChatGPT under its strict digital rules and closer legal scrutiny by designating it as a "very large" online platform, marking a first for an artificial intelligence chatbot.

Brussels also designated the Reddit forum and the popular gaming network Roblox under the same category, a label that comes with additional obligations and oversight.

"ChatGPT, Reddit and Roblox will now be held to a higher standard of scrutiny and accountability in the European Union, in line with their large impact on our citizens and society," EU technology chief Henna Virkkunen said.

The "very large" designation applies to platforms and search engines with more than 45 million monthly active users in the 27-nation bloc, a threshold ChatGPT, Reddit and Roblox reported meeting, the commission said.

The three now have four months to comply with additional obligations under the Digital Services Act (DSA), a content law that is a major weapon in the legal armoury the EU has deployed to rein in Big Tech in recent years.