The pope has called for an Easter truce in Ukraine and, in an apparent reference to Russia, questioned the value of planting a victory flag “on a heap of rubble”.

He spoke at the end of a Palm Sunday service for about 50,000 people in St Peter’s Square, the first time since 2019 that the public was allowed to attend following two years of scaled back services because of Covid restrictions.

“Put the weapons down! Let an Easter truce start. But not to rearm and resume combat but a truce to reach peace through real negotiations open to some sacrifices for the good of the people,” the pope said.

“In fact, what kind of victory would be one that plants a flag on a heap of rubble?”

A flare-up of pain in his knee forced the pope, 85, to miss the traditional procession from the obelisk at the centre of the square to the altar on the steps of St Peter’s basilica.

Instead he watched on seated at the altar and limped as he said the Mass.

He evoked the horrors of war in his homily, speaking of “mothers who mourn the unjust death of husbands and sons … refugees who flee from bombs with children in their arms … young people deprived of a future … soldiers sent to kill their brothers and sisters”.

Since the war began in Ukraine, the pope has only mentioned Russia specifically in prayers, such as during a special global event for peace on 25 March. But he has referred to Russia by using terms such as “invasion” and “aggression”.

Moscow describes the action it launched on 24 February a “special military operation”. The pope has rejected that terminology, calling it a war.

Some people in the crowd put small Ukrainian flags at the tip of their olive branches and a woman who read one of the prayers near the altar was dressed in blue and yellow.