Equity markets tumbled on Thursday after Donald Trump delivered a "haymaker" blow with sweeping tariffs against US partners and rivals, fanning a global trade war that many fear will spark recessions and ramp up inflation.

In Hong Kong, the Hang Seng Index ended the day down 1.52 percent at 22,849.81.

The Hang Seng China Enterprises Index slid 1.31 percent to end at 8,420.14, and the Hang Seng Tech Index dropped 2.09 percent to 5,313.26.

Tokyo's Nikkei briefly collapsed more than four percent, while US futures plunged with oil prices, safe haven gold hit a record high and the dollar retreated amid worries retaliatory measures will batter economies.

Stephen Innes of SPI Asset Management said: "President Trump walked into the Rose Garden and detonated the most aggressive trade shock the market's seen in decades. This isn't a jab – it's a full-on haymaker."

Wall Street "had talked itself into a softer, more symbolic move.

"Instead, Trump carpet-bombed the global supply chain.

"This was a 'shock and awe' tariffs campaign, dressed up in 'reciprocity' language but designed to throttle the trade deficit through brute force."

Innes said the measures meant inflation risks had surged and economic growth expectations would be cut, with the Federal Reserve "pinned between a hawkish rock and a deflationary hard place".

Tokyo pared its hefty drop but still ended down 2.8 percent, while Sydney, Seoul, Manila, Mumbai, Shanghai and Singapore also fell.

However, Wellington managed to eke out a small gain as New Zealand faced smaller tariffs.

London, Paris and Frankfurt all tumbled more than one percent, while Vietnam's stock exchange dived 7.8 percent after the country was hit with levies of almost 50 percent.

Wall Street futures were also battered, with the Dow dropping two percent, the Nasdaq plunging more than three percent and the S&P 500 off 2.8 percent off.

Safe havens rallied as traders sought to dump risk assets.

Gold hit a new peak of US$3,167.84 and the yen strengthened to 147.04 per dollar from 150.50 the day before.

Among other currencies, the euro and pound both jumped more than one percent against the dollar on fears about the US economy and bets that the Fed will have to cut interest rates to deal with the impact on growth.

Among the big corporate losers, Sony shed 4.8 percent, while its South Korean rival Samsung was down 2 percent.

Car titan Toyota was off more than five percent, Nissan lost 3.7 percent and Honda was down 2.3 percent.

Tokyo-listed tech investment firm SoftBank was off close to four percent.

Hong Kong-listed e-commerce giants fell after the removal of a duty-free exemption for small parcels from China.

Alibaba and JD.com shed 5 and 5.2 percent respectively. (AFP/Xinhua)