SEOUL, South Korea — South Korea’s top infectious disease expert has pleaded people over 65, pregnant women and other medically vulnerable individuals to stay at home as officials struggle to trace and stem the spread of the coronavirus amid increased public activity.

Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention, made the comments on Monday while addressing 24 new cases linked to a group of churches near capital Seoul.

She also raised concern over the hundreds of transmissions linked to workplaces, including call centers and at least one massive warehouse.

“We have been seeing an increased number of high-risk patients, who have been infected through family members or religious gatherings,” Jeong said. “There’s a particular need for people over 65 years in age, pregnant women and those with chronic medical conditions to be alert,” she added, recommending that they avoid face-to-face gatherings with others.

South Korea has so far reported more than 11,000 cases and around 270 deaths.

Christian churches have been campaigning for worshippers to return since authorities eased social distancing guidelines in mid-April, but the resurgence in COVID-19 cases in the greater capital area in past weeks has pushed officials to restore some controls.

Incheon, a port city west of Seoul, on Monday banned gathering at more at some 4,200 churches and other religious facilities. Gyeonggi Province, which surrounds the capital, issued an administrative order to shut down warehouses, funeral homes and wedding halls, but city officials didn’t immediately confirm how many businesses were affected.