Prisoners took to the roof of a Milan jail Monday as part of more than 20 violent country-wide protests against coronavirus measures, in which six convicts have died.
In another incident, around 50 inmates broke out of jail in the southern city of Foggia, media reports and officials said. The justice ministry said 43 had been recaptured.
By Monday evening, inmates who ran riot in a prison in Melfi, a town in Italy's south between Naples and Bari, were holding four officers hostage in two high-security sections, the justice ministry said.
In Rieti, about 70 kilometres (around 40 miles) northeast of Rome, "the entire institution is occupied by prisoners," the ministry said in a statement.
Some prisoners have been asking to be granted amnesty over the health crisis.
Rights campaigners warned of mass revolts over the new measures, and families gathered outside prisons to protest at the restrictions -- and to get news of their loved ones.
Around a dozen prisoners at the San Vittore prison in Milan managed to climb onto the roof of one of the wings and shouted slogans as police and prison guards below looked on.
It was the second day of unrest, with 22 jails -- from Venice and Milan in the north, to Rome, Naples and Bari in the south -- protesting by Monday over measures aimed at preventing the virus entering the prison system.
Six inmates died during or following clashes at Sant'Anna jail in the city of Modena in northern Italy, according to prisoner rights group Antigone.
Three died in Modena, while the other three died after being transferred from there to jails in Parma, Alessandria and Verona, Italian news agency ANSA said.
It said there were reports that the prisoners had broken into a medical centre in the Modena jail and had overdosed.
Authorities in Modena would not immediately confirm the reports.
- 'Situation could deteriorate' -
At San Vittore, prisoners covering their faces with scarves or bandanas perched precariously on the slanted roof tiles. Fellow inmates could be seen massed around the barred windows at the jail in the Italian capital.
Relatives rallied outside many of the concerned jails in protest over the measures, including a ban on family visits.
"We're urging inmates and relatives to stop violent protests, as they could spark others," Antigone's Andrea Oleandri said.
"The situation could rapidly deteriorate."
Prisoners, who get most of their information from televisions, tended to protest in solidarity if they saw convicts in other jails rioting, Oleandri said.
Family members desperate for news of their loved ones had to be held off by prison guards at the entrance to the Modena jail, as ambulances and prison vans came and went, an AFP photographer said.
"This rumpus, this 'war' happened because the inmates hadn't been given any information about what was going on outside, and visits had been suspended," said Gilberto, the father of one prisoner who did not want to give his last name.
"No-one's telling us who's died, who is injured, or why they died and why they were injured," the 59-year-old told AFP.
Italy's prisons are suffering from overcrowding, with over 61,000 inmates locked up in spaces designed to hold just 51,000.
- 'Fear of virus' -
The country has been hard hit by the virus -- with 366 fatalities so far -- and the government has imposed draconian measures to stop it spreading further, including placing large swathes of the north under lockdown.
As well as halting visits and limiting day releases, all prison staff are supposed to have their temperatures checked on arrival each day. Medical checks for incoming inmates have also been ramped up, Antigone said.
"The prisoners are worried the virus will get into jail and spread," Oleandri said.
"They are in confined spaces. There are usually two or three people in a 12-metre square cell. And while visits have been suspended, there are still lots of people coming and going," he said.
Antigone has called for more inmates with only a short time left to serve to be allowed to do so at home, reducing the numbers behind bars.
Amnesty International Italy said it was "deeply concerned" by the violence and stressed that the "critical hygienic-sanitary conditions" in jails demanded the utmost precautions be taken to limit the risk of contagion.