Israeli police with face masks and batons and backed by surveillance helicopters have stepped up patrols of ultra-Orthodox Jewish neighbourhoods that have become coronavirus hotspots.
This week has seen tense altercations, and some rabbis have admitted that their communities, where prayer and scripture study are traditionally communal, are not observing new social distancing regulations.
A few days ago in Bnei Brak, a city near Tel Aviv with a largely ultra-Orthodox population, hundreds of faithful crowded together to attend the funeral of prominent rabbi Tzi Shenkar.
They flouted pandemic emergency rules limiting attendance at funerals to 20 people, who must keep a distance of at least two metres (six feet) from one another.
The orders have closed places of worship of all faiths.
The mass funeral brought wide condemnation, including from some high-profile members of the ultra-Orthodox community.
Eliyahu Sorkin, head of intensive care at Bnei Brak's Mayanei Yeshua hospital and himself ultra-Orthodox, called the breach of health regulations "criminal".
Influential rabbi Chaim Kanievsky condemned the mass event and Health Minister Yaakov Litzman, also ultra-Orthodox, even said he had asked Prime Minister Benjamin Netanyahu to impose a blockade on the city.
"The situation there is horrific," the minister said in an interview with Israeli daily Yediot Aharonot.
"Every day there is fear of losing lives."
- 'Missed the boat' -
The government was said to be considering the blockade request.
In Jerusalem, Chief Rabbi David Lau made a radio appeal to the observant to "inform" the authorities of those they see breaking the rules.
Litzman's ministry has so far confirmed more than 4,800 cases of COVID-19 infection nationwide since the first recorded instance in Israel, in February.
Since then 17 people have died and more than 160 have recovered, according to data released Tuesday.
Media reports say that half of the country's sick are ultra-Orthodox, although they make up only around 10 percent of the population.
Bnei Brak, where the mayor himself tested positive for COVID-19, runs second in the number of confirmed cases after Jerusalem.
The Holy City is the heart of the Orthodox world, centred round the densely-populated Mea Sharim neighbourhood which has largely become a no-go zone for outsiders.
There and in other ultra-Orthodox neighbourhoods, police helicopters hover over lanes, courtyards and alleys, looking for men gathering for outdoor prayer now that synagogues are locked down.
Police said officers on the ground had handed out fines to violators on Monday.
Police in Mea Sharim arrested ultra-Orthodox men who protested the closure of a synagogue there, an AFP photographer witnessed.
Video shows an officer briefing his squad to sweep the area and ensure that all places of prayer were closed, while some objectors shouted "Nazis".
Rabbi Henri Kahn told AFP that the ultra-Orthodox world had "missed the boat" in anti-virus measures.
"We did not want to see," he said.
In Bnei Brak in particular, some synagogues and seminaries stayed open well after the lockdown orders given by the authorities.
- No TV, no internet -
Motti Ravid, director of the Mayanei Yeshua hospital there, expects a sharp rise in the number of ultra-Orthodox who become infected.
He says that with internet and television prohibited in the community on religious grounds, government directives took a long time to filter through.
Even for those using mobile phones, access to the internet and most instant messengers is blocked, shutting them off from the main means of communication used now by the health ministry.
Kahn also said that the government measures directly clashed with Jewish religious obligations, such as the requirement for every man to pray three times a day in a synagogue with nine others.
Next week is the major Jewish holiday of Passover, a feast also known as the festival of freedom which celebrates the biblical Exodus from Egypt.
At its centre is feasting and reciting blessings with the extended family.
Many now wonder how to observe the ancient traditions at a time of social distancing, while officials fear mass breaches of the safety regulations.
As the holiday nears, said health ministry director general Moshe Bar Siman Tov, "we are afraid that people will gather on Passover despite the ongoing ban, and that the situation will worsen."