US stock futures and Asian share markets have tumbled, while the yen jumped to four-month highs against the dollar after North Korea fired a missile over northern Japan, fuelling worries of fresh tension between Washington and Pyongyang.

S&P mini futures fell as much as 0.85% on the news before paring losses to trade 0.55% down.

Yesterday the index was little changed as investors tried to assess the fallout from Tropical Storm Harvey.

European shares are expected to fall, with spread-betters looking at a lower opening of 0.5% to 0.6% for Britain's FTSE, France's CAC, and Germany's DAX.

Japan's Nikkei was down 0.9% to a four-month low at one point, then pared losses to be 0.5% off.

South Korea's Kospi shed as much as 1.6%, helping to drag down MSCI's broadest index of Asia-Pacific shares outside Japan 0.6%.

"All sectors are tumbling, which clearly shows that North Korea risks are the reasons behind it," said Cho Byung-hyun, a stock analyst at Yuanta Securities in Seoul.

North Korea fired a missile early this morning that flew over Japan and landed in the Pacific about 1,180km off the northern region of Hokkaido, in a sharp escalation of tensions on the Korean peninsula.

North Korea has conducted dozens of ballistic missile tests under young leader Kim Jong-Un, but firing projectiles over mainland Japan is his first.

"The missile flew across Japan this time, so the implications will likely be a bit different from previous ones," said Hirokazu Kabeya, chief global strategist at Daiwa Securities.

North Korea threatened earlier this month to fire missiles into the sea near the US Pacific territory of Guam, a host to major US military installations, after President Donald Trump warned Pyongyang would face "fire and fury" if it threatened the United States.

The yen rose 0.8% to 108.33 to the dollar, its highest since April, despite Japan's proximity to North Korea.

The yen tends to benefit during times of geopolitical or financial stress as Japan is the world's biggest creditor nation and there is an assumption that Japanese investors will repatriate funds should a crisis materialise.

The safe-haven Swiss franc hit a one-month high of 0.9498 franc to the dollar and last traded at 0.9523 franc on the dollar, up 0.3%. The Swiss currency gained 0.4% versus the euro to 1.1396 per euro.

The euro hit a 2 1/2-year high of $1.1986 and last stood at $1.1970, maintaining its uptrend after European Central Bank chief Mario Draghi did not express concern about the currency's recent rise in his speech at Jackson Hole.