Former minister of interior Matteo Salvini s lawyer Giulia Bongiorno arrives at Palermo s court to attend a trial, in Palermo, Saturday, Oct. 23, 2021. AP
Salvini attended the opening hearing in Sicily's Palermo, which came a month after it was first postponed.
The hearing was expected to be largely procedural, with Judge Roberto Murgia expected to decide on the admissability of witness lists sought by both sides.
Salvini, the leader of the far-right League party who is known for an "Italians first" policy, is charged with kidnapping and abuse of office for using his position as interior minister to detain the 147 migrants at sea in August 2019.
The 48-year-old has said that the decision was not his alone, but agreed by the government, including by the then-prime minister, Giuseppe Conte.
Prosecutors have asked that the witness list include Conte, as well as Italy's current Interior Minister Luciana Lamorgese and Foreign Minister Luigi Di Maio.
Salvini tweeted a photo of himself inside the courtroom, standing in front one of the cells used for some defendants.
"This is the courtroom of the Palermo prison. The trial wanted by the left and by the fans of illegal immigration begins: how much will it cost the Italian citizens?" he tweeted.
Outside the courtroom, the founder and director of the Spanish charity Open Arms that operated the rescue ship said the trial was not politically motivated.
"Saving people isn't a crime, but an obligation not only by captains but by the entire state," Oscar Camps told journalists.
The beginning of the trial came as 406 migrants rescued in various operations off the coast of Libya by the German charity ship Sea Watch 3 arrived at the Sicilian port of Pozzallo to be disembarked.
'Closed ports' policy
In the 2019 Open Arms case, migrants were finally allowed to leave the vessel after six days, following an order by the prosecutor's office. A subsequent onboard inspection revealed serious overcrowding and dire sanitary conditions.
Salvini has staunchly defended himself, saying he was protecting the country with his "closed ports" policy, which aimed to stop people attempting the dangerous Mediterranean crossing to Italy.
Italy's Senate voted last year to strip Salvini of his parliamentary immunity, paving the way for the trial.
A related case in which Salvini, 48, was accused of blocking other migrants at sea on an Italian coastguard boat was thrown out by a court in Catania earlier this year.
Salvini's League takes a hard line on migrants, arguing that Italy bears an unfair burden as the first point of entry into Europe for those arriving from northern Africa.
When he blocked the ships, Salvini was part of a coalition government and held the positions of interior minister and deputy prime minister.