US Secretary of State Hillary Clinton has expressed concern over the disappearance of Laotian civil society activist Sombath Somphone and has urged Laos to conduct a “transparent investigation”.
"We call upon the Lao government to pursue a transparent investigation of this incident and to do everything in its power to bring about an immediate and safe return home to his family," Clinton said in a statement.
Human rights groups in the country said they fear he was abducted by pro-government forces.
Mr Somphone was a social activist who campaigned for fair land rights for farmers, which may have riled the communist government.
The government has denied any knowledge of his whereabouts.