The strongest condemnation of abortion was issued by Pope Francis, who called it a symptom of a "throwaway culture" that placed too little value on human life.
The pope, who has focused more on social issues such as poverty than on abortion since becoming pontiff in March, said it was "frightful" to think about the early termination of pregnancy.
Francis made the remarks in a wide-ranging speech to the Vatican diplomatic corps in which he condemned violence in Syria and other flashpoints around the world, saying peace was threatened by "every denial of human dignity".
"We cannot be indifferent to those suffering from hunger, especially children, when we think of how much food is wasted every day in many parts of the world immersed in what I have often termed 'the throwaway culture'," the pope said.
"Unfortunately, what is thrown away is not only food and dispensable objects, but often human beings themselves, who are discarded as 'unnecessary'. For example, it is frightful even to think there are children, victims of abortion, who will never see the light of day."
Pope Francis has spoken out on abortion far less than his predecessor Benedict XVI, and drew criticism from some conservative Catholics when he used his first interview as pope to call for "mercy" toward homosexuals, divorced people and women who have abortions.