European markets were set to open lower on Monday morning, as North Korea’s latest nuclear test prompted investors to rush to safe-haven assets.

The FTSE 100 is seen 19 points lower at 7,426; the Dax is expected to open down by 59 points at 12,083 and the CAC 40 is set to open 23 points lower at 5,097.

On Sunday, North Korea conducted its sixth and most powerful nuclear test to date, which it claimed was of an advanced hydrogen bomb for a long-range missile.

In response to Pyongyang’s test, South Korea carried out a live-fire exercise simulating an attack on North Korea. The missile drill saw ballistic missiles launched from fighter jets and from the ground. It came as U.S. Defense Secretary James Mattis warned that any threat from North Korea towards the U.S. or its allies would be met with a “massive military response.”

The United Nations Security Council is poised to hold an emergency meeting later on Monday to discuss its response. The Japanese yen, gold and sovereign bonds all rose as growing international unease caused a typical knee-jerk shift to save havens.

Meantime, the leaders of Brazil, Russia, India, China and South Africa will continue to discuss economic ties in Xiamen, China on Monday. The three-day gathering, which began on Sunday, brings together the five fast-growing economies.

Chancellor Angela Merkel appeared to hold her ground in a live television debate against political rival Martin Schulz on Sunday, just three weeks before the German general election. Merkel was seen 14 points ahead of Schulz in opinion polls before the debate. A survey by Infratest Dimap showed Merkel emerged as the clear winner on Monday, as her overall performance in the debate was viewed as more convincing by 55 percent, compared to 35 percent for Schulz.

Elsewhere, U.S. markets are closed for Labor Day on Monday.