Italy reported four more deaths Tuesday from prison riots linked to the new coronavirus that have now officially claimed 11 lives over three days.

The justice ministry has blamed all the deaths on drug overdoses that occurred after prisoners broke into medical storage rooms. The claim was impossible to immediately verify through independent sources.

Jails have been ordered to stop visits and limit day releases as part of a broader government response to a disease that has killed 463 people in Italy in just over two weeks. Some prisoners have been asking to be granted amnesty over a health crisis that had infected more than 9,000 people across the Mediterranean country.

The justice ministry said the situation in most of the 23 jails hit by rioting since Sunday has been brought back under control.

"The unrest that affected more than 20 prisons (Monday) has ended almost everywhere," the justice ministry said in a statement. "In many of them, the protests and occupation... by prisoners have ended and the inmates have returned to their sleeping quarters."

The ministry said three of Tuesday's deaths occurred in the Rieti prison some 70 kilometres (around 40 miles) northeast of Rome. "Initial findings suggest that the deaths may have been caused by the reckless taking of drugs," the justice ministry said.

Another convict also died in the Modena prison near the northern city of Bologna. The ministry said eight people have died there in all. The last Modena death "also presumably resulted from a drug overdose," said the ministry. "The unrest (in Modena) has ended," the ministry added.

It said four security personnel and a health official who had been taken hostage by rioters in Melfi in the south of Italy had all been released. But it said 22 convicts who escaped the Foggia prison near Italy's southeastern coast were still on the run.

'Combustible situation'

Italy's prisoner rights ombudsman Mauro Delma blamed the riots on prison overcrowding and fears about the rapidly spreading disease. "It seems that containment measures recommended for all citizens are not acceptable to prisoners who are already facing prison overcrowding," Delma told the RAI News 24 channel. "This scenario makes for a combustible situation," the ombudsman said.

AFP reporters saw around a dozen prisoners at the San Vittore prison in Milan climb onto the roof of one of the wings and shout slogans Monday as police and prison guards below looked on. There were similar scenes at several other prisons as rioters wearing scarves and bandanas over their faces climbed roofs and shouted slogans to television news crews hovering in helicopters overhead. Relatives rallied outside many of the concerned jails in protest over the measures.