JERUSALEM (BLOOMBERG) - Israel postponed the reopening of its borders to foreign tourism until Aug 1, as it tries to snuff out a surge of coronavirus infections it attributes largely to the incursion of the highly transmissible Delta variant.

"We have decided to treat this as a new outbreak. We intend to cut it off here, take a pail of water and douse the flames while they are still small," Prime Minister Naftali Bennett said late on Tuesday (June 22), after a tour of the national airport.

In addition to delaying the return of incoming tourism by a month, the government on Wednesday reinforced quarantine regulations, ordered more daily testing and introduced a 5,000 shekel (S$2,065) fine on parents whose children do not quarantine when required.

Mask wearing, scrapped just days ago, was reimposed at airports, border crossings and medical facilities, and will be required in all closed public places if new daily infections fail to fall below 100 soon.

New cases were down to the single digits in the middle of this month, but this week topped 100 for three days straight. Most of the new cases have been unvaccinated children and people returning from abroad.

Some of the sick had been fully vaccinated with the Pfizer-BioNTech vaccine.

While the Delta Covid-19 strain, first reported in India, is the most infectious to date, almost all cases in Israel have been asymptomatic or mild.

Mr Bennett's swift action pointed to a lesson learnt from Israel's devastating experience under then premier Benjamin Netanyahu, when a low caseload following a first lockdown led to an abandonment of caution. New infections ballooned to more than 11,000 a day, sparking two more lockdowns and tamed only by the world's most aggressive vaccination campaign.

More than half of Israel's population has been inoculated. Israel approved vaccines for 12- to 15-year-olds early this month, but only several thousands have been immunised.

Still, hospitals that were previously overrun are now treating only a few dozen Covid-19 patients.

Professor Eran Segal, a Weizmann Institute scientist, told 103FM radio that while there was no immediate need for panic, Israel did need to monitor developments.

On his Twitter page, Prof Segal said that despite the uptick in infections, "there are still practically no cases of severe illness".