HONG KONG, July 13 (Xinhua) -- Hong Kong decided on Monday to tighten anti-epidemic measures again, such as mandatory mask-wearing and closures of entertainment venues, as a record number of local COVID-19 cases were reported after loosening of such policies.

Chief Executive of the Hong Kong Special Administrative Region (HKSAR) Carrie Lam announced the decision Monday evening at a press conference, hours after the Center for Health Protection (CHP) reported 41 new local infections, a new high since the COVID-19 outbreak.

Hong Kong will introduce a new regulation that makes it mandatory for passengers to wear face masks in public transport facilities including taxis and buses since Wednesday.

The group gathering limit, which was relaxed to 50, will return to four for 14 days since Wednesday. In a week also starting Wednesday, twelve types of venues, such as fitness rooms and game centers, will be closed, and restaurants will not be allowed to provide dining-in services after 6:00 p.m. local time.

Border control will also become stricter to prevent imported cases, as inbound visitors, who have traveled to high-risk areas during the past 14 days, should have tested negative for the new coronavirus before boarding flights to Hong Kong.

Hong Kong witnessed a resurgence of COVID-19 cases over the past weeks after some control and preventive measures were eased to revive the economy and let residents resume normal lives.

At a press conference earlier on Monday, Chuang Shuk-kwan, head of the CHP's Communicable Disease Branch, said the epidemic situation was grave as cases with unknown sources increased every day and warned that there may be more such cases in the community.

Of the new local infections on Monday, the transmission chains of 20 cases were still unclear and 21 cases were related to patients diagnosed previously. Taking account of 11 imported cases, the COVID-19 tally in Hong Kong rose to 1,521.

The CHP noted that numerous new cases were related to restaurants and thus urged residents to avoid meal gatherings and keep social distancing.

In response to the spike of cases, the government had already tightened social distancing measures, such as resuming the cap on the number of customers in a restaurant and allowing schools to begin summer vacation earlier.

The Hong Kong Trade Development Council (HKTDC) decided to postpone four upcoming public events on Monday, including a week-long book fair starting Wednesday, a sports and leisure expo and an education and careers expo.

The HKTDC said it will likely be difficult to perform contact tracing and imposing subsequent disease control measures for the expected huge number of visitors in the events. The book fair in 2019 attracted nearly 1 million visitors.

Ocean Park and Hong Kong Disneyland, Hong Kong's two iconic theme parks that just reopened in mid-June after months of closure, will suspend operation again for a week since Wednesday.

Lam said Hong Kong will step up virus-test efforts and expects the testing capacity of public institutions to reach 8,000 samples a day next month.

The government also plans to introduce two mainland private institutions to help virus tests, which can hopefully start tests for more than 400,000 high-risk people this week, including staff members of nursing homes and restaurants and taxi drivers, Lam said.