Prisoners have taken to the roof of a prison in the Italian city of Milan as part of a series of violent country-wide protests against coronavirus measures, in which six inmates have died.
In another incident, around 50 inmates broke out of jail in the southern city of Foggia, and about 20 are on the run after their fellow convicts were caught, Italian media reported.
Jails have been ordered to stop all visits and limit day releases.
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 inmates at least 23 jails - from Venice and Milan in the north, to Rome, Naples and Bari in the south - protesting over measures aimed at preventing the virus from 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 added 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.
Domenico Pianese, head of the police union Coisp, said the mass revolts looked planned and warned that the mafia could be behind such "an evident strategy to try to take advantage of the difficulties caused by the coronavirus".
'Situation could deteriorate' - human rights group
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," Andrea Oleandri of Antigone 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, Mr Oleandri said.
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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 said.
Italy's prisons are suffering from overcrowding, with over 61,000 inmates locked up in spaces designed to hold just 51,000.
Prisoners fear virus 'will get into jail and spread'
The country has been hard hit by coronavirus - 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," Mr 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 added.
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.