One worker was killed and six other workers are missing after being swept away by swift currents on Monday while removing old water pipes inside a water distribution reservoir near the Han River, police said.

Cho Ryong-geun, 57, who was killed in the incident, is known to be Chinese. Work to rescue the six others -- including three workers also believed to be Chinese -- is currently underway.

Water from the rain-swollen Han River, which flows through the center of Seoul, rushed into the nearby 48-meter-high reservoir at around 5:30 p.m. after heavy rainfall. The ill-fated workers were removing old water pipes at the bottom of the reservoir at that time, according to the police.

As the underground work site is 1.5 km long, rescue efforts will remain challenging until the level of water is lowered through drainage, police said.

"The six workers appear to be be trapped in the tunnel, and we will be able to make rescue efforts after the water is drained," a rescue worker said. "As of now, there is nothing to do." 

The heavy rainfall has battered mostly northern parts of the country in recent days, including Gyeonggi Province and surrounding Seoul, killing three people and displacing 200 others. (Yonhap News)