Seoul - South Koreans were treated to a rare weather phenomenon on Monday when yellow snow fell in the capital and elsewhere across the country.

But the snow -- containing dust or sand from the desert regions of northern China -- could pose a health hazard, the country's meteorological office warned.

"It's tough to say whether it's yellow sand mixed in snow or if it's snow mixed in yellow sand," a met official told Reuters.

A high concentration of the dust particles prompted the weather bureau to issue a yellow dust warning for the second time in three days.

South Korea frequently gets sand or dust storms, but a yellow snow storm is very rare.

"I have never seen yellow snow falling before," the met official said.

The agency said the yellow snow was a health hazard and officials have warned that the pollutants in the flurries included heavy minerals.