Italy's Foreign Minister Franco Frattini confirmed the release of his country's citizens on state television on Tuesday.
It later emerged that a US-led occupation special forces unit had freed the men, though details are shrouded in secrecy.
Salvatore Stefio, Umberto Cupertino and Maurizio Agliana had been held in Iraq for almost two months but have been freed in good condition.
The four Italian security workers were originally seized on 12 April near Baghdad, but Fabrizio Quattrocchi was shot dead after Italy refused to bow to demands it withdraw all troops from Iraq.
Italy has some 2700 troops based in the southern town of Nasiriya, the third-biggest occupation contingent after the US and Britain.
A Polish construction company employee in Baghdad has also been released.
The 64-year-old Jerzy Kos was seized on 2 June. His work colleague taken at the same time was able to escape.
Polish firm Jedynka said the abductors arrived in two jeeps at the company's office in a flat and took the two Poles and five Iraqi staff, including security guards, prisoner.
An Iraqi resistance group calling itself the Green Brigade has said it was behind the detentions
A Turkish man has also been freed in on Tuesday but another Turk abducted with him the previous day remained in captivity, the Turkish embassy in Baghdad said.
The embassy initially said both Tarkan Arikoglu and Adnan
Azizoglu had been freed, but later said only the latter had been released.