Tokyo led most Asian markets lower Tuesday, hit by a stronger yen as investors fled to safety following a suspected terror attack in Saint Petersburg that left 11 people dead and fanned fresh geopolitical concerns.

The blast on a metro train in Russia's second city dragged US and European equities lower after a positive start to the week across Asia. 

Russia said it was probing the explosion as a possible terror attack, while on Tuesday, Kyrgyzstan's security services said a suicide bomber from that country was responsible.

The tragedy comes after four people were killed outside parliament in London last month in an attack claimed by Islamic State.

Traders are also on edge about the upcoming summit between Chinese President Xi Jinping and Donald Trump.

Trump at the weekend said he expects the meeting with Xi in Florida "will be a very difficult one". It follows a series of attacks by him on Beijing's trade policies and accusations it is a currency manipulator.

A world rally fuelled by hopes for Trump's overall economic agenda sputtered last month, despite a series of strong economic readings from China to Europe and the United States.

"Markets are at an interesting juncture at the moment," said Greg McKenna, chief market strategist at AxiTrader, in a note. "It's caught between what has been a real pick-up in data over the past four months and some fading notions about the effectiveness of Donald Trump and his ability to implement his agenda."

He added that while Trump's failure to pass his repeal of Obamacare last month was seen by some as a chance to concentrate on his tax reforms, most investors worry about the prospects of pushing through promised economy-boosting measures.

"The question for traders and markets more broadly is what comes next," McKenna said.

- Toshiba routed again -

Tokyo ended 0.9 percent lower, with Toshiba collapsing almost 10 percent -- extending Monday's 5.5 percent slump following reports it may have to delay releasing its earnings for October-December for a third time. They were first due in mid-February.

Toshiba has delayed formally reporting its earnings because of problems at US nuclear unit Westinghouse, which last month filed for bankruptcy. Regulators have given Toshiba until April 11 to publish the results and there are concerns it could be removed from the stock exchange.

Sydney and Seoul each shed 0.3 percent and Singapore gave up 0.2 percent. However, Wellington added 0.3 percent and Manila soared 1.3 percent

Hong Kong and Shanghai were closed for public holidays.

On currency markets the dollar dipped against the yen, sitting around 110.45 yen, well down from levels around 111.30 yen in Asia Monday.

The Russian ruble stabilised against the dollar, having swung wildly Monday soon after news of the Saint Petersburg explosion.

But the South African rand shed almost two percent after Standard & Poor's cut its rating on the country to "junk" owing to "heightened political and institutional uncertainties" following President Jacob Zuma's decision to sack top ministers last week, including respected finance minister Pravin Gordhan.

The unit had already fallen more than 10 percent since March 27, when speculation started swirling that Gordhan's job was in danger.

Other key events this week include the March US jobs report and the release of minutes from the most recent meetings of the Federal Reserve and European Central Bank.

In early European trade London rose 0.3 percent, Paris edged up 0.1 percent and Frankfurt was flat.

- Key figures at 0700 GMT -

Tokyo - Nikkei 225: DOWN 0.9 percent at 18,810.25 (close)

London - FTSE 100: UP 0.3 percent at 7,303.48

Hong Kong - Hang Seng: Closed for public holiday

Shanghai - Composite: Closed for public holiday

Euro/dollar: DOWN at $1.0657 from $1.0671

Pound/dollar: DOWN at $1.2450 from $1.2484

Dollar/yen: DOWN at 110.45 yen from 110.91 yen

Oil - West Texas Intermediate: DOWN 24 cents at $50.00 per barrel

Oil - Brent North Sea: DOWN 26 cents at $52.86

New York - Dow: DOWN 0.1 percent at 20,650.21 (close)

Source: AFP