"Suicide is an amazing public health problem. There is one suicide every 40 seconds -- it is a huge number," said Shekhar Saxena, director of WHO's mental health department, at the presentation of the report in Geneva.
"Suicide kills more than conflicts, wars and natural catastrophes," he said.
"There are 1.5 million violent deaths every year in the world, of which 800,000 are suicides."
Some of the highest rates of suicide are found in central and eastern Europe and in Asia, with 25 percent occurring in rich countries, the report says.
Men are almost twice as likely as women to take their own lives. Common methods are hanging, gunshots, and especially in rural areas the use of poisonous insecticides.
"Globally, suicide rates are highest in people aged 70 years and over. In some countries, however, the highest rates are found among the young," WHO said.
"Notably, suicide is the second leading cause of death in 15-29 year-olds globally."Don't glamorise suicide
Alexandra Fleischmann, one of the report's co-authors, said part of the blame lies with the publicity given to suicides by famous people, such as Hollywood actor Robin Williams.
The Oscar-winning star, who had suffered from depression, was found dead at his home on August 1, prompting an outpouring of emotion from the public and widespread media coverage.
Ella Arensman, president of the International Association for Suicide Prevention, said that after news broke of Williams' death she received "five emails of people who had recovered (from a) suicide crisis and saying that they are thinking again about suicide."
"These overwhelming reports can have a contagion effect on vulnerable people," she said, referring also to the "sharp increase" in suicides after German football player Robert Enke killed himself in 2009.
"Suicide should not be glamorised or sensationalised," Fleischmann said, urging news outlets not to mention suicide as the cause of death at the start of reports, but only at the end, "with a mention of where (the reader) can find help."
WHO, which called suicide a major public health problem that must be confronted and stemmed, studied 172 countries to produce the report, which took a decade to research.
It said that in 2012 high-income countries had a slightly higher suicide rate -- 12.7 per 100,000 people, versus 11.2 in low- and middle-income nations.
But given the latter category's far higher population, they accounted for three-quarters of the global total.
Southeast Asia, including North Korea, India, Indonesia and Nepal, made up over a third of the annual figure.
WHO cautioned that suicide figures are often incomplete, with many countries failing to keep proper tallies.
In addition, "there are many suicide attempts for each death," WHO chief Margaret Chan said.
"The impact on families, friends and communities is devastating and far-reaching, even long after persons dear to them have taken their own lives," she added.
Suicide and attempted suicide are considered a crime in 25 countries, mostly in Africa, in South America and in Asia.
The most suicide-prone countries were Guyana (44.2 per 100,000), followed by North and South Korea (38.5 and 28.9 respectively).
Next came Sri Lanka (28.8), Lithuania (28.2), Suriname (27.8), Mozambique (27.4), Nepal and Tanzania (24.9 each), Burundi (23.1), India (21.1), and South Sudan (19.8).
Next were Russia and Uganda (both with 19.5), Hungary (19.1), Japan (18.5), and Belarus (18.3).
The UN agency said its goal is to cut national suicide rates by 10 percent by 2020. A major challenge, it said, is that suicide victims are often from marginalised groups of the population, many of them poor and vulnerable.
However, "suicides are preventable," Chan said.