European stocks finished lower on Monday as the euro hit its highest level against the dollar in more than two years, while energy shares declined in the wake of refinery shutdowns prompted by then-Hurricane Harvey that pummeled Texas. Trading was closed on the FTSE 100 UKX, -0.08% as the U.K. observed the August Bank Holiday, meaning trading volumes were lighter than usual.

Investors sought out havens, boosting assets such as the Japanese yen, gold and U.S. Treasurys, after North Korea fired a ballistic missile over Japan for the first time since 2009. The launch represented an "unprecedented, grave and serious threat" to Japan, said chief government spokesman Yoshihide Suga.

U.S. stock-index futures were sliding lower late Monday in New York, with futures for the Dow down nearly 110 points at its nadir, after reports that North Korea fired a ballistic missile that flew over Japanese airspace, reigniting geopolitical tensions that had cooled between North Korea and U.S. allies in the Pacific Rim.