HONG KONG — China's spiraling Delta variant outbreak has reached Wuhan, the original epicenter of the pandemic, prompting citywide coronavirus testing as authorities scramble to contain the city's first reported local infections in more than a year.

China is grappling with its worst outbreak in months, with more than 300 cases detected in more than two dozen cities across the country. The country now has 144 medium- and high-risk areas, the most since the initial outbreak in early 2020, the National Health Commission said Wednesday.

The speed and scale of the spread has spurred mass domestic travel restrictions, with all inter-city coach, taxi and online car-hailing services suspended in medium- and high-risk areas. Chinese immigration authorities have also vowed to "strictly restrict non-urgent, unnecessary cross-border travel," including tightening the issuing of passports for Chinese citizens.

On Monday, seven infections were reported among migrant workers in Wuhan, the central Chinese city where the coronavirus was first detected in December 2019. As of Wednesday, a total of 20 local infections have been reported, including 8 asymptomatic cases, according to the Hubei provincial health commission.

The city of 11 million people was placed under the world's first and arguably strictest coronavirus lockdown in January 2020, during the height of its devastating initial outbreak. The paralyzing 76-day lockdown came at a huge personal cost to residents but eventually succeeded in taming the virus. Wuhan had not reported any locally transmitted cases since May last year.