South Korean authorities have placed a cat shelter in the capital Seoul under quarantine after detecting the H5N1 strain of avian influenza in two cats at the facility, Reuters reported, citing the country's agriculture ministry.

There have been no cases of the highly pathogenic avian influenza reported in humans in South Korea, the ministry said.

It was the first time since 2016 that avian influenza had been detected in a cat in the country, the ministry said in a statement issued on Tuesday.

The two cats that tested positive for H5N1 were among 38 that have recently died at the shelter, news agency Yonhap reported.

H5N1 has spread among poultry and wild birds for years but there have been sporadic outbreaks reported globally in mammals such as cats, mink and otters.

The World Health Organization has said that the risk to humans from H5N1 remains low, but said reports of infections in mammals needed to be "monitored closely".

Three UN agencies this month warned that an ongoing rise in avian influenza outbreaks globally raised concerns that the virus might adapt to infect humans more easily, and urged countries to strengthen disease surveillance and improve hygiene at poultry farms.

Nobody who had come into contact with the cats at the Seoul shelter was showing symptoms of the disease and those who made contact and are considered to be at higher risk would be monitored for 10 days, the ministry said.