LONDON—A terrorist killed two people in a stabbing attack in the heart of London before being shot dead by police, U.K. officials said, prompting authorities to lock down a busy area on the edge of the financial district and bringing back memories of a 2017 rampage nearby. In a separate incident Friday evening, three people were wounded in a stabbing on a busy shopping street in the center of The Hague, Netherlands. Dutch police said the motive wasn’t immediately clear and that the suspect got away. Authorities in London called the attack there terrorism but offered no further details on...