US stocks have suffered steep falls with the top index tanking to a six-month low shortly after opening, as Donald Trump's tariffs reverberated through the world's financial markets.The S&P 500 plummeted about 4% to 5,440 shortly after markets opened in Wall Street - hitting the lowest level since September.The Dow Jones tumbled around 3.6%, while the technology-focused Nasdaq index plunged nearly 5%.

US stocks have suffered steep falls with the top index tanking to a six-month low shortly after opening, as Donald Trump's tariffs reverberated through the world's financial markets.The S&P 500 plummeted about 4% to 5,440 shortly after markets opened in Wall Street - hitting the lowest level since September.The Dow Jones tumbled around 3.6%, while the technology-focused Nasdaq index plunged nearly 5%.