"I express my own and the government's great satisfaction for the liberation, under bail conditions, of our marines. An important objective has been reached," Monti said in a statement.
"But the final outcome, for which we have worked with determination since the start in our relations with Indian authorities of every level, is the return of our marines to Italy," he said.
Massimiliano Latorre and Salvatore Girone, who shot dead two fishermen off India's southwestern coast on February 15, were freed on bail by Kochi High Court last week, and left jail today for a hotel.
The marines, who deny murder and say they mistook the fishermen for pirates, appeared in court in the southern state of Kerala today for a preliminary hearing in a case that has caused a diplomatic row.
The court fixed June 18 for the next hearing.
The pair were employed to guard against pirate attacks on an Italian oil tanker. They have said the fishermen's boat behaved suspiciously and ignored warning shots while approaching the Italian vessel.
They were freed on bail on condition they each deposit personal bonds of 10 million rupees (USD 178,000) and comply with other conditions, including surrender of their passports.
Italy has called the case against the marines illegal and challenged it before India's Supreme Court. It has also paid compensation of 144,000 euros (USD 190,000) to the fishermen's families. The Kerala government has ruled out any out-of-court settlement in the murder case.