A U.N. report on the increase in peacekeepers killed in violent attacks blames many of the fatalities on inaction in the field and "a deficit of leadership" from U.N. headquarters to remote locations.

It urges greater initiative, determination, action and use of force when necessary declaring: "Nobody attacks a stronger opponent."

The report says that "casualties have spiked" since 2013, with 135 soldiers, police and civilians in the U.N.'s 15 far-flung peacekeeping missions killed by acts of violence, "more than during any other five-year period in history."

The report released Monday was authorized by Secretary-General Antonio Guterres, funded by China and led by retired Brazilian Lt. Gen. Carlos Alberto dos Santo Cruz, a former commander of U.N. peacekeepers in Haiti and Congo, and retired U.S. Army Col. William Phillips.