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.