Vatican City - Pope Benedict said on Tuesday states had to set ethical limits to what can be done to protect their people from terrorism and that some countries have flouted international humanitarian law in recent wars.
The Pope made his comments in his annual message for the Roman Catholic Church's World Day of Peace, which is celebrated on January 1.
In the message, which is traditionally sent to governments and international organizations, he also repeated his often stated belief that war in God's name is never justified.
In the 14-page document, the Pope also decried other threats to peace, such as hunger, poverty, environmental harm and regimes he said were persecuting Christians or imposing a single religion on their people.
"...the new shape of conflicts, especially since the terrorist threat unleashed completely new forms of violence, demands that the international community reaffirm international humanitarian law, and apply it to all present-day situations of armed conflict, including those not currently provided for by international law," he wrote.
He called for a review of what states could ethically do to protect their citizens while still trying to respect international humanitarian law, "which has not been consistently implemented in certain recent situations of war."
International human rights groups have criticized the U.S. government over its treatment of terror suspects at a base in Guantanamo Bay, Cuba and the practice of "rendition," or flying terrorist suspects to third countries for interrogation.
"...the scourge of terrorism demands a profound reflection on the ethical limits restricting the use of modern methods of guaranteeing internal security," he wrote.
The Pope, in the second peace message of his pontificate, appeared to acknowledge that fighting terrorism posed a difficult moral dilemma for governments.
"Increasingly, wars are not declared, especially when they are initiated by terrorist groups determined to attain their ends by any means available," he wrote.
"In the face of the disturbing events of recent years, states cannot fail to recognize the need to establish clearer rules to counter effectively the dramatic decline what we are witnessing," he said.
He specifically mentioned the conflict in southern Lebanon, where he said "the duty to protect and help innocent victims and to avoid involving the civilian population was largely ignored." He did not name either Israel or Hizbollah guerrillas.
He said the desire by some states to acquire nuclear weapons had thrown humanity back to the "profound anxieties of the Cold War period."
He also described hunger, abortion, experimentation on human embryos and euthanasia as "an attack on peace".
"The duty to respect the dignity of each human being, in whose nature the image of the Creator is reflected, means in consequence that the person can not be disposed of at will," the pope writes.
"As far as the right to life is concerned, we must denounce its widespread violation in our society: alongside the victims of armed conflicts, terrorism and the different forms of violence, there are the silent deaths caused by hunger, abortion, experimentation on human embryos and euthanasia. "
In a section on religious freedom, he decried "regimes that impose a single religion on everyone." This was apparent reference to Saudi Arabia, where non-Muslims are not allowed to practice their faith in public.