Houses are partially submerged in floodwaters in Asuncion, capital of Paraguay, in this Dec 20, 2015 file photo. [Photo/Agencies]

ASUNCION/BUENOS AIRES - More than 100,000 people have had to evacuate from their homes in the bordering areas of Paraguay, Uruguay, Brazil and Argentina due to severe flooding in the wake of heavy summer rains brought on by El Nino, authorities said on Saturday.

In the worse affected country, Paraguay, around 90,000 people in the area around the capital city of Asuncion have been evacuated, the municipal Emergencies Office said. Many are poor families living in precarious housing along the banks of the River Paraguay.

The Paraguayan government has declared a state of emergency in Asuncion and seven regions of the country to free up funds to help those affected. Several people have been killed by trees falling in the storms that caused the flooding, local media reported. There was no official death toll yet.

People travel on a boat near flood-affected houses in Asuncion, capital of Paraguay, Dec 27, 2015. [Photo/Agencies]

In Alberdi, some 120 kilometers (75 miles) south of Asuncion, the government recommended that several thousand more people living along the banks of the River Paraguay evacuate.

"(The flooding) was directly influenced by the El Nino phenomenon which has intensified the frequency and intensity of rains," the national Emergencies Office said.

This year's "El Nino," which sparks global climate extremes, is the worst in more than 15 years, the UN weather agency, the World Meteorological Organization (WMO), said last month.

"Severe droughts and devastating flooding being experienced throughout the tropics and sub-tropical zones bear the hallmarks of this El Nino, which is the strongest in more than 15 years," WMO chief Michel Jarraud said in a statement.

Officials at Paraguay's Emergencies Office said the river might rise even more in the coming days, stabilizing and falling back towards normal levels from January onwards.