Bullion hit another record Tuesday while the dollar weakened and equities fluctuated as US President Donald Trump's latest salvo against Federal Reserve boss Jerome Powell added fuel to fears about the central bank's independence.

With the US tariff blitz still causing ructions on global trading floors, investors are now dealing with the added worry that the US president will try to remove the country's top banker.

Trump took a swipe at Powell last week for his warning that the sweeping levies would likely reignite inflation, saying his "termination cannot come fast enough" and adding that "I'm not happy with him. I let him know it and if I want him out, he'll be out of there real fast, believe me."

While that raised eyebrows, the Republican tycoon sent shivers through markets Monday by calling on the Fed boss again to make pre-emptive cuts to interest rates and calling him a "major loser" and "Mr Too Late."

He said on his Truth Social platform that there was "virtually" no inflation, claiming energy and food costs were well down and pointed to the several reductions by the European Central Bank.

The outbursts have fanned concern that Trump is preparing to oust Powell, with top economic adviser Kevin Hassett saying Friday the president was looking at whether he could do so.

Panicked Wall Street investors once again dumped US assets, with all three main indexes ending down around 2.5 percent on Monday.

"The first volley on Thursday had little market reaction, but Monday's second barrage has seen an intensification of the 'sell America trade'," said National Australia Bank's Tapas Strickland.

"Whether or not President Trump is legally able and willing to move against the US Fed, the jousting underscores the loss of US exceptionalism and the very real policy risk for investors."

The rush for safety saw gold hit yet another record above $3,500, and while the dollar steadied after the previous day's selloff, it remained under pressure against its major peers.

Stocks swung between gains and losses on the first full day of business after the Easter break.

Tokyo, Sydney, Seoul, Wellington, Taipei, Manila and Bangkok fell while Hong Kong, Shanghai, Singapore, Mumbai and Jakarta rose.

London was barely moved, while Paris and Frankfurt edged down.

However, analysts warned of another rout if Trump were to try to fire the Fed boss, which many said could cause a crisis of confidence in the US economy.

"Were Powell to be fired, the initial reaction would be a huge injection of volatility into financial markets, and the most dramatic rush to the exit from US assets that it is possible to imagine," said Pepperstone strategist Michael Brown. 

"Lower, much lower, equities; Treasuries sold across the board; and, the dollar falling off a cliff. 

"Any sign of the longstanding, independent nature of the Fed coming under threat would see investors across the globe selling every single US-based asset that they have, and also poses the genuinely scary prospect of upending the entire way in which the global financial system operates."

Key figures at 0715 GMT

Tokyo - Nikkei 225: DOWN 0.2 percent at 34,220.60 (close)

Hong Kong - Hang Seng Index: UP 0.6 percent at 21,527.95

Shanghai - Composite: UP 0.3 percent at 3,299.76 (close)

London - FTSE 100: FLAT at 8,275.99

Euro/dollar: DOWN at $1.1500 from $1.1510 on Monday

Pound/dollar: UP $1.3389 at $1.3377

Dollar/yen: DOWN at 140.38 yen from 140.89 yen 

Euro/pound: DOWN at 85.88 pence from 86.03 pence

West Texas Intermediate: UP 1.1 percent at $63.78 per barrel

Brent North Sea Crude: UP 1.0 percent at $66.95 per barrel

New York - Dow: DOWN 2.5 percent at 38,170.41 (close)