TEMPO.CO, Tokyo - Japan's COVID-19 death toll topped the 10,000-mark on Monday. Previously on Sunday, a third state of emergency was declared in Tokyo and the western prefectures of Osaka, Kyoto and Hyogo.

One year after Japan confirmed its first COVID-19 case, the nationwide death toll from the virus stood at 5,000, according to public broadcaster NHK.

Infectious disease experts warned that Japan is now battling a "fourth wave" of infections including highly-contagious variants of the virus.

The complete lifting of the second state of emergency in April saw the mortality rate begin to rise after being on a downtrend, health ministry data showed.

Meanwhile, according to data cited by Kyodo News, the COVID-19 mortality rate increases with age, with 13.9 percent of those in their 80s and above dying, followed by 5.2 percent of those in their 70s, and 1.5 percent in their 60s.

With more than 3,300 new infections reported nationwide on Monday, 900 of which in the hard-hit western prefecture of Osaka, the government is trying to curb the spread of the virus by encouraging people to work from home.

But according to NHK, mobile phone data has shown around 40 percent more people were around Tokyo station during rush hours on Monday morning, compared with the Monday average during the first state of emergency declared around a year ago.

In the capital city of Tokyo, 425 new cases were confirmed on Monday, down from the 635 cases reported Sunday.

However, on Saturday, the country's new cases over the past 24 hours surged to 876, marking the highest number of daily infections since the second state of emergency was lifted in late March.

Under the new COVID-19 restrictions, large commercial facilities, theme parks and movie theaters have been ordered temporary closures.

In addition, restaurants, bars serving alcohol, karaoke parlours, movie theaters and stadiums have been asked to suspend their operations, and department stores have been asked to only keep departments selling essential items open.

The 17-day emergency period covers the Golden Week, a string of national holidays.

The government is discouraging travel during one of the most popular time for Japanese people to take vacations, and has urged people to refrain from crossing prefecture borders in a bid to curb the spread of the virus.

"I am sorry to cause people so much inconvenience. But please remind yourself how things were a year ago when the first state of emergency was in place. I must ask you to curb outings more drastically this time," Yasutoshi Nishimura, the minister in charge of the government's COVID-19 response, said as the state of emergency came into effect.

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