Pope Benedict XVI celebrated an open-air Mass Sunday for tens of thousands of pilgrims from across the Middle East, saying Christians must do their part to end the "grim trail of death and destruction" in the region.

"I appeal to you all to be peacemakers," Benedict said.

Pope Benedict spoke from an altar built on land reclaimed with debris from Lebanon's 1975-1990 civil war, pressing ahead with his call for peace and reconciliation between Christians and Muslims.

He said that justice and peace are needed in building "a fraternal society, for building fellowship".

Helicopters flew overhead and soldiers set up roadblocks and patrolled streets in central Beirut.

The crowd cheered and waved tiny Vatican and Lebanese flags as Benedict arrived in his bullet-proof popemobile at the Mass site on the Beirut waterfront.

Benedict has been appealing for tolerance and religious freedom.

At a meeting with young people Saturday evening, the pope said he admired the courage of Syrian youth and that he did not forget their suffering.

The papal visit comes amid soaring sectarian tensions in the region, exacerbated by the conflict in Syria, which is in the throes of an 18-month-old civil war.