Lisbon, Aug 31 (IANS): A helicopter crash near the Douro River in the Samodaes region in northern Portugal has claimed the lives of four soldiers, with one still missing, according to local media reports.

The helicopter, which was carrying six people, including a pilot and a team of five soldiers, crashed while returning from firefighting operations in northern Portugal on Friday, reported Xinhua news agency, quoting Lusa News Agency.

The accident occurred at approximately 12:50 p.m. when the helicopter plunged into the Douro River.

The pilot was rescued by a passing boat and is currently reported to be in a stable condition under medical observation at a hospital, with no apparent risk to his life.

However, search and rescue operations continue for the remaining missing soldier.

Portuguese Prime Minister Luis Montenegro addressed the nation after the tragedy, expressing profound sorrow for the loss of lives.

"Today is a very sad day for Portugal," said Montenegro. "Our thoughts and prayers are with the families of the victims, and we extend our deepest condolences to the National Republican Guard (GNR) for this tragic loss."

He also announced that the government, in agreement with President Marcelo Rebelo de Sousa, has declared Saturday, August 31, a national day of mourning.

The Portuguese President cancelled his plans and immediately travelled to the site of the accident to oversee the ongoing search and rescue efforts.

The cause of the crash is still under investigation by the Office for the Prevention and Investigation of Aircraft and Railway Accidents (GPIAAF).