Pope Francis is presiding over a Good Friday procession at Rome's Colosseum. It is his first major Holy Week religious service drawing a large outdoor crowd since the Brussels attacks prompted heightened security across Europe.

Hours earlier, police led explosives-detecting dogs through inspections inside and outside the ancient arena.

Clutching candles and prayer books, thousands of people stood on a cool evening during the torch-lit procession in Rome. Faithful from around the world were taking turns carrying a plain, lightweight cross to recall Jesus' suffering at crucifixion. Police waved metal-detecting wands across pilgrims and searched their bags and knapsacks.

Francis was expected to speak after some two hours of reflections on meditations read aloud. During past Way of the Cross processions at the Colosseum, pontiffs have denounced the world's evils.