Tokyo Gov. Yuriko Koike said Monday that a citywide lockdown may become “the only option left” if various measures fail to prevent an explosive rise in the novel coronavirus in the capital.

“Cities around the world are in lockdown,” Koike said during a news conference Monday. “In Tokyo there is serious concern that clusters of infected individuals will lead to an explosive increase in the number of cases in the city. If that were to happen, we may have no choice but to impose strict isolation measures — a so-called lockdown — to prevent further spread.”

Despite ongoing measures to promote social distancing, as well as school closures and the cancellation of major public events, Tokyo was described as a region “at significant risk of further outbreaks” during a meeting of the government’s expert panel last week. According to an estimate by the health ministry, Tokyo could see upwards of 530 positive cases by April 8.

An additional 17 individuals were confirmed on Tuesday to have tested positive for the novel coronavirus, the largest number of cases the city has seen in a single day — breaking the record set just a day earlier.

As of Monday, Tokyo has reported 154 cases of infection and four deaths. Of those that tested positive, 101 were hospitalized, 31 of whom have subsequently been discharged. Koike warned that the next three weeks are critical, as Tokyo could see an “overshoot,” or an explosive increase in cases.

“It goes without saying that Tokyo is the biggest city in Japan and serves as a gathering place for businesses, universities and people from around the world,” the governor said. “Because of this, the city is at great risk of experiencing clusters of infection emerging among youth.”

But it’s impossible to decipher whether the governor is truly considering a citywide lockdown, or simply mentioning such a possibility to frighten people into complying with efforts to prevent the virus from spreading further, said urban planning expert Hiroo Ichikawa.

“Shutting down Tokyo would be a massive ordeal,” he said. “The question is now whether Koike means it and specifically what she has in mind, or if she’s using it as a warning to scare people into taking the pandemic seriously.”

Several cities in northern Italy, parts of New York City and London, as well as countless other places around the world, are experiencing varying degrees of restrictive measures in order to prevent the virus from further spreading. On Tuesday, China lifted its lockdown on Wuhan, the city thought to be the origin of the novel coronavirus, nearly four months after the first cases were reported.

A lockdown in Tokyo would most likely come in phases and begin with the public transportation system, Ichikawa said. While Tokyo Metro and the East Japan Railway Co. are privately owned, they would surely heed Koike’s request if she were to call on them to scale back or shut down traffic, he said.

This would be followed by the prohibition of mass gatherings, Ichikawa went on.

Italy quickly placed several towns under lockdown, going as far as to fine or imprison violators and deploy the military to stand guard. The question arises whether the Tokyo Metropolitan Government or the national government have the authority, or the ability, to enforce such strict rules.

The short answer is no, according to Koju Nagai, a lawyer based in Hyogo Prefecture.

While municipal leaders can request or demand in varying degrees that residents stay indoors or schools temporarily close, they can’t enforce penalties on those who refuse to comply, Nagai said.

Over the weekend, despite Tokyo’s warnings against it, massive crowds gathered in local parks to see the cherry blossoms in full bloom. Countless public events have also been canceled in a bid to avoid mass gatherings during a festive time of the year when young adults graduate from school and start their first jobs.

“It’s unclear if Koike is envisioning a lockdown of the city’s functions or the movement of people,” Ichikawa said. “Hopefully she’ll specify what she meant, and what such an unprecedented decision might entail, in the coming days.”

RELATED PHOTOS Tokyo Gov. Yuriko Koike holds a news conference about the coronavirus at the Tokyo Metropolitan Government Building on Monday. | RYUSEI TAKAHASHI