So far 68 asylum seekers are confirmed dead after a fishing boat that departed from Turkey broke up in rough seas off Italy's southern coast.
The boat is believed to have been carrying up to 200 passengers.
Around 80 people survived, with the final death toll feared to be much higher.
The head of state then went to the San Giovanni di Dio di Crotone hospital, where 15 survivors are being treated, including several children.
The president also sent toys to the paediatric ward.
He appeared particularly moved as he was applauded by citizens, with some shouting, “president, we want justice and truth”.
Sources said the victims' relatives asked for help repatriating the bodies as well as support for the survivors.
Mattarella vowed to give that support, adding that the situation of Afghani refugees was a priority, the sources said.
Meanwhile, Democratic Party leader Elly Schlein also visited Crotone.
She met with the mother of two children who died, and a third recovering in hospital.
Through tears, she recounted the ordeal and asked Schlein to help find the bodies of her children.
Democratic Party senator Francesco Verducci, who was with Schlein, wrote on Facebook of the moving scenes in Crotone of citizens paying tribute to the victims.
“Outside the gates there are flowers and cards left by school children,” he wrote.
“There is an unspeakable pain, people are lining up [to pay their respects].
“It’s as if humanity itself was in those coffins.
“They are not foreigners. They are us.”
The Crotone Public Prosecutor's Office has asked the Coast Guard and the Guardia di Finanza for documents related to their activities in the hours before the shipwreck.
ANSA
