Chinese AI assistant DeepSeek has become the top rated free app on Apple's App Store in the US and elsewhere, beating out ChatGPT and other rivals. It's powered by the open-source DeepSeek V3 model, which reportedly requires far less computing power than competitors and was developed for under $6 million,

Shares in major tech firms such as Nvidia fell sharply, with the chip giant losing almost $600bn (£482bn) in market value. What has shaken the industry is DeepSeek's claim that its R1 model was made at a fraction of the cost of its rivals - raising questions about the future of America's AI dominance and the scale of investments US firms are planning.