(Reuters) - ChatGPT developer OpenAI's weekly active users surged past 400 million in February, a company spokesperson told Reuters on Thursday, highlighting rapid growth in the adoption of artificial intelligence tools.

The Microsoft ( MSFT )-backed startup had 300 million weekly active users in December. Its paying business users also crossed 2 million in February, more than doubling from its last update in September.

The upbeat numbers come weeks after China's DeepSeek launched an AI model it said could match or even outperform Western rivals at a fraction of the cost, stirring doubts about U.S. dominance in the generative AI space.

But a surge in demand for DeepSeek since then has caused outages at the small startup.

There have also been questions around how DeepSeek was able to obtain Nvidia's H800 chips, used to train AI models, even though Washington had banned their exports to China.

OpenAI reported a twofold increase in developer traffic for its reasoning models over the last six months and a fivefold surge for its o3 model since its launch in late January.

The news about OpenAI's weekly users was first reported by CNBC earlier in the day.

(Reporting by Rishi Kant in Bengaluru; Editing by Devika Syamnath)