LONDON — Save the Children UK says in a report released Tuesday that it has uncovered evidence of widespread sexual abuse of children at the hands of peacekeepers and international aid workers in war zones and disaster areas. The report said more than half the children interviewed knew of cases of coerced sex and improper sexual touching and that in many instances children knew of 10 or more such incidents carried out by aid workers or peacekeepers. In some cases, children as young as 6 years old were abused, the report said.