Beijing has tightened entry restrictions after new reports of local infections of COVID-19 in various regions across China, local authorities said at a presser on Sunday.

Inbound travelers from areas with locally-transmitted cases must provide negative nucleic acid results within two days and undergo a 14-day health observation after arriving in Beijing, said Pan Xuhong, deputy head and spokesperson of the municipal public security bureau.

People from cities that have positive cases are advised not to travel to Beijing if it's not urgent, Pan said.

From 12:00 p.m. Saturday to 3:00 p.m. Sunday, Beijing recorded five new COVID-19 cases including a case with light symptoms and four with mild symptoms. There is also an additional asymptomatic case. So far, Beijing has recorded 15 COVID-19 cases including an asymptomatic one.

Gene sequencing results showed the Delta variant is responsible for the latest emerging COVID-19 cases, the Beijing Center for Disease Prevention and Control reported. The results also showed the virus detected in cases in Beijing is extremely similar to the virus detected in the recent cases in Inner Mongolia Autonomous Region and Gansu Province, indicating these cases are all connected.

Wu Liangyou, deputy head of the National Health Commission's Disease Control and Prevention Division, said the gene sequencing research and results showed the virus from recent cases is different from the previous cases in the country, which means these cases were caused by a new case imported from outside of China.

Wu predicted the case number may continue to rise as more cases will be discovered due to the ongoing mass screening being conducted in several cities, which also could affect a larger area.