Pope Benedict XVI marked the Catholic Church's 46th World Day of Peace on Tuesday by recalling the world's conflict hotspots, from Syria to Nigeria, and by speaking out against selfishness, inequality and unregulated capitalism.
The 85-year-old pontiff was greeted in Rome's St Peter's Square by some 10,000 people who had taken part in a global march for peace.
Organized in 650 cities around the world, the march was designed to remind people of the 18 conflicts that continue to ravage the Middle East, Africa and Asia.
These include Syria, where a civil war has raged for nearly two years; Afghanistan, where Taliban insurgents continue to fight international and Afghan forces; and Nigeria, where the Boko Haram Islamist sect has killed an estimated 1,400 people - many of them in attacks on Christians - since it started its campaign against the central government and Western lifestyles in 2010.
Presiding over a New Year mass earlier in the day, the pontiff also spoke out against the "growing instances of inequality between rich and poor" as well as "the prevalence of a selfish and individualistic mindset which also finds expression in an unregulated financial capitalism."
Humanity's desire for peace, the pope told the Catholic Church hierarchy and ambassadors to the Holy See gathered in St Peter's Basilica, is a "fundamental moral principle" and a gift from God.
The German-born pontiff also used his new Twitter account to bless his estimated 2 million followers in various languages.
After what the Vatican has described as a year marked by personal "sadness" over the so-called Vatileaks scandal - which saw his former butler blow the whistle on scheming and suspected corruption at the highest levels of the Catholic Church - the pope has a busy agenda in store for 2013.
During the first half of the year, the pope will issue his fourth encyclical, likely on the subject of faith. In July, he will take part in World Youth Day celebrations in Brazil, his second visit to the country with the world's largest Catholic population, while in October he is expected to create 802 saints in a single day, a new record for the Catholic Church.