Japan plans to dramatically ramp up daily COVID-19 tests, borrowing from anti-contagion measures used during the recent Tokyo Olympics, as it battles its worst wave of infections, driven by the delta variant.

New infections exceeded 25,000 on Thursday for the first time, media reports said, with the surge mainly among those in their 40s and 50s, most of whom are unvaccinated.

The speed and severity of Japan's delta-driven infections are overtaking the strategy of targeted cluster tracing it has favored over the mass testing used by many nations.