Nearly a week after Congo's government announced the kidnapping of two United Nations experts along with their translator and drivers, no trace of them has been found.
Their abduction in a region of the country where kidnappings are rare, and where the experts were investigating abuses by state and militia forces, has raised alarm as political tensions spread over an election crisis.
Michael Sharp of the United States and Zaida Catalan of Sweden were abducted with three Congolese colleagues while traveling by motorcycle through Central Kasai province. It was not clear when exactly the kidnapping occurred.
It is the first recorded abduction of international workers in the province, a region far from the usual turmoil in eastern Congo where multiple armed groups roam.
A new report by the UN secretary-general has warned that violence and threats to civilians have spread to new parts of the vast country because of Congo's prolonged political crisis.
President Joseph Kabila's mandate ended in December, but he has stayed on as presidential elections once set for last year have been delayed. A political agreement reached between the ruling party and opposition after weeks of deadly protests promises an election by the end of this year and that Kabila will not run.
But the new report by UN chief Antonio Guterres says the agreement is in peril as the sides engage in "brinksmanship." Further delays in implementing the deal "will only serve to inflame tensions and fuel the violence that is now spreading across the country," the report says.
Parts of Congo have experienced insecurity for more than two decades since the end of the Rwandan genocide led to the presence of local and foreign armed militias, all vying for control of mineral-rich land.