Pope Francis sets out to defend weak, poor and the environment in first mass

Pope Francis has urged the princes, presidents, sheiks and thousands of ordinary people gathered for his installation mass to protect the environment, the weakest and the poorest as he set out his priorities as leader of the world's 1.2 billion Catholics.

The Argentinian – the first pope from Latin America and the first named after St Francis of Assisi – said a little bit of tenderness could "open up a horizon of hope".The Vatican said between 150,000-200,000 people attended the mass, held under bright blue skies after days of rain.In Buenos Aires, thousands of people packed the central Plaza de Mayo square to watch the celebration on giant TV screens. They erupted in joy when Francis called them from Rome, his words broadcast to the crowd over loudspeakers."I want to ask a favour," Francis told them. "I want to ask you to walk together, and take care of one another … and don't forget that this bishop who is far away loves you very much. Pray for me."Francis was interrupted by applause several times during his homily, including when he spoke of the need to protect the environment, serve one another with love and not allow "omens of destruction", hatred, envy and pride to "defile our lives".

He said the role of the pope was to open his arms and protect all of humanity: "Especially the poorest, the weakest, the least important, those whom Matthew lists in the final judgment on love: the hungry, the thirsty, the stranger, the naked, the sick and those in prison."Today amid so much darkness we need to see the light of hope and to be men and women who bring hope to others," he said. "To protect creation, to protect every man and every woman, to look upon them with tenderness and love, is to open up a horizon of hope, it is to let a shaft of light break through the heavy clouds."Francis, 76, thrilled the crowd at the start of the mass by getting out of his jeep to bless a disabled man. It was a gesture from a man whose short papacy so far is becoming defined by such spontaneous forays into the crowd and concern for the disadvantaged.The blue and white flags from Argentina fluttered above the crowd, which Italian media initially estimated could reach 1 million. Civil protection crews closed the main streets leading to the square to traffic and set up mile-long barricades to try to control the throng and allow official delegations through.