NEWYou can now listen to Fox News articles! The U.S. embassy in London on Friday warned Americans to "exercise increased caution" while visiting Jewish and American areas in the U.K. and in Europe because of a recent rise in threats."The U.S. Embassy in London notes recent attacks and threats targeting Jewish and American institutions in the United Kingdom and Europe," the alert said. "U.S. citizens, particularly those visiting institutions serving Jewish or American interests, should remain alert and exercise increased caution."The embassy further advised Americans to remain alert while visiting tourist and expat areas and houses of worship, review personal security plans and to check local media...