The U.S. State Department warned Americans to “exercise increased caution” due to a heightened risk of terrorism in Sri Lanka after at least 290 people were killed and some 500 more injured in coordinated attacks on tourist hotels and Christian churches Sunday morning. “Terrorist groups continue plotting possible attacks in Sri Lanka,” a new travel advisory warned late Sunday. “Terrorists may attack with little or no warning, targeting tourist locations, transportation hubs, markets/shopping malls, local government facilities, hotels, clubs, restaurants, places of worship, parks, major sporting and cultural events, educational institutions, airports, and other public areas.” At least 37 international tourists were killed, including “several” Americans, the State Department said.