GENEVA, Oct. 21 (Xinhua) -- Record flooding has hit two-thirds of South Sudan, affecting over 900,000 people, the UN refugee agency UNHCR said on Friday.

UNHCR spokesperson Boris Cheshirkov told a press briefing in Geneva that the Sudanese capital Bentiu has become an island surrounded by floodwaters.

All roads in and out of the city were flooded, with boats and the airstrip serving as lifelines for humanitarian aid to reach the 460,000 people already displaced by both flooding and conflict.

He called for international support for humanitarian efforts in the country, in the face of a fourth consecutive year of record-breaking rains, with worse to come as the climate crisis accelerates.

"Camps for the internally displaced are below the current water level, protected from floodwaters only by dikes -- large, compacted mounds of earth -- erected by the United Nations, the government, and the inhabitants themselves," he said.

There is an increasing need for food, shelter, water, and sanitation supplies, Cheshirkov added.

According to UNHCR, South Sudan's refugee crisis is the largest in Africa, with over 2.3 million South Sudanese refugees having fled to neighboring countries.

Meanwhile, an estimated 2.2 million people were internally displaced within the country, which also hosts over 340,000 refugees.

Wracked by civil war for most of its brief history, South Sudan is afflicted by widespread intercommunal violence, the devastating effects of climate change, and severe food insecurity affecting 60 percent of its population of 11 million. - Xinhua