HONG KONG -- South Sudan nationals will need a visa to enter Hong Kong from Thursday, including those in transit at the airport, Hong Kong's Immigration Department said here on Monday.

Currently South Sudan nationals are not required to secure a visa for remaining on the airside in transit.

"With a view to ensuring a proper balance between facilitating the entry of genuine visitors and the need to safeguard the integrity of immigration control, the visa policy is subject to constant review and changes will be introduced if circumstances so warrant," an Immigration Department spokesman said.

Hong Kong has adopted an open visa policy, under which nationals of about 170 countries and territories may visit Hong Kong visa-free for periods ranging from seven to 180 days, the spokesman said.