Abe said at a news conference that Japan is at critical juncture to determine whether the country can keep the outbreak under control ahead of this summer's Tokyo Olympics.

Abe, whose announcement this past week of a plan to close all schools for more than a month through the end of the Japanese academic year sparked public criticism, said the emergency package includes financial support for parents and their employers affected by the school closures.

He said that much about the virus is still unknown, and that "fighting against an unknown and unclear enemy is not easy."

"Frankly speaking, this battle cannot be won solely by the efforts of the government," Abe said. "We cannot do it without understanding and cooperation from every one of you, including medical institutions, families, companies and local governments."

He said he understands that closing schools through the end of March would spoil celebrations for students who are graduating and would cause parents to have to take extra days off from work. But he said the step was necessary to minimize the risk of children and teachers developing mass infections.

Abe called on the public to understand his school plan, and promised to provide support from the emergency package, especially for parents who may have to miss work to take care of their young children. The economic package also includes measures to amplify medical preparedness in case of an escalation of the outbreak, and help in the development of vaccines and more efficient virus testing kits.

Abe also urged companies to accommodate the needs of workers who might have trouble finding outside help to look after their young children during school closures.

Japan has at least 940 confirmed cases of the virus, including 705 from the Diamond Princess cruise ship, whose quarantine in Yokohama led to international criticism that the containment was ineffective. Several of about 1,000 former passengers who tested virus-free and were allowed to get off the ship after a 14-day quarantine have since tested positive.

Abe's government has also been criticized for being slow to act in the early stages of the outbreak, allowing tens of thousands of Chinese tourists into Japan before imposing limited travel bans.