Kenyan security forces hunting for Somali gunmen and two Spanish aid workers they kidnapped found their vehicle abandoned in the desert as aid agencies scaled back relief operations in the world's biggest refugee camp.
Kenya has deployed troops and six helicopters to try to rescue the pair, who have apparently been forced to continue on foot with their captors. They had been heading towards Somalia.
The head of the Spanish office of their aid group, Doctors Without Borders, said on Friday that the group had had no contact with the workers after they were seized on Thursday.
Juan Antonio Bastos identified the women as Montserrat Serra i Ridao, 40, from Girona in north-east Spain, and Blanca Thiebaut, 30, from Madrid.
Mr Bastos called for discretion from the international media and said his organisation so far had no idea where the women were being held.
The United Nations temporarily suspended all non-lifesaving aid operations in the Dadaab refugee camp following the kidnappings, a spokeswoman said.
Hundreds of staff are confined to their offices, forcing the cancellation of services such as education, counselling and relocation of families until further notice.
"Only water, food and health services are being maintained," said UN refugee agency spokeswoman Needa Jehu-Hoyah. "This will of course have an impact on the poor refugees."
In recent months tens of thousands of refugees fleeing a spreading famine in southern Somalia have swollen the severely overcrowded camp. Most of the nearly half-million people in Dadaab, a sprawling, dusty wasteland about 50 miles from the Somalia-Kenya border, are refugees from Somalia's 20-year-old civil war.
Now many refugees are afraid that services might stop permanently following the kidnappings, said refugee community leader Mohamud Jama Guled. "People are sad and mournful," he said. "They have gone to the (Doctors Without Borders) hospital but it is not opening ... They hope these two ladies will come back. Anyone who takes these humanitarians, they are wrong. They are wrong forever. These people are helping those who are suffering."