Daily infections nationwide topped 10,000 for the first time on Thursday, with Tokyo reporting a record 3,865 cases.
“Infections are expanding in the Tokyo and western metropolitan areas at an enormous speed that we have never experienced before,” Prime Minister Yoshihide Suga said.
Should the spike continue at the current pace with the spread of the more contagious delta variant, Japan’s medical system could collapse, he added.
The emergency measures will be extended until the end of August, after the Olympics and well into the Paralympics which begin on August 24.
Critics pointed out that the upsurge in cases in Tokyo, where the Games are held, happened despite over two weeks of emergency measures.
Japan recorded 15,166 fatalities from the virus, including 2,288 in Tokyo, since the pandemic began.