The Japanese government is eyeing an extension of coronavirus emergency measures in Tokyo and eight other prefectures following calls from governors. Experts warn that a dangerous variant could spread rapidly through the capital.
Tokyo's battle against the virus has seen slow results.
While new infections are declining --- the daily average for the past week remains high, at around 600.
Experts suggest over 80 percent were infected by a more contagious strain first found in the UK.
Even more concerning is a cluster of infections linked to a variant that has crippled hospitals in India. Given situations abroad, experts warn that the strain could become more common.
Tokyo Governor Koike Yuriko said, "We're still at the beginning of our vaccination rollout, so we have no choice but to continue to take thorough anti-virus measures."
Emergency declarations for Tokyo, Osaka and seven other prefectures are set to expire on Monday.
Government officials plan to make a final decision on an extension on Friday, after consulting a panel of experts.
Health authorities across Japan confirmed more than 4,100 new cases on Thursday and 106 deaths.