Global markets have fallen after a tech sell-off that fuelled Wall Street's worst day in a month and weak economic data in China showing an unprecedented slump in investment. Japan's tech-heavy Nikkei fell 1.8% on Friday, South Korea's Kospi plunged 2.6% and there was a 1.5% fall in Australia, after a torrid day on Wall Street as Nvidia and other tech companies tumbled over valuation concerns.