Kenyan security forces hunting for Somali gunmen and two kidnapped Spanish aid workers found their vehicle abandoned and mired in the desert as aid agencies scaled back relief operations in the world's biggest refugee camp Friday in response to the abduction there.

Kenya has deployed troops and six helicopters to try to rescue the pair, who apparently have been forced to continue on foot with their captors. They had been headed toward Somalia.

The head the Spanish office of their aid group, Doctors Without Borders, said Friday in Madrid that the group has had no contact with their workers after they were seized Thursday.

Juan Antonio Bastos identified the women as Montserrat Serra i Ridao, 40, from Girona in northeast Spain and Blanca Thiebaut, 30, from Madrid.

Bastos called for discretion from the international media and said his organization for the moment had no idea where the women were being held.

The U.N. 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 like education, counseling and relocation of families until further notice.

"Only water, food and health services are being maintained," said U.N. 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 (80 kilometers) 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 as a result of 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."

Gunmen seized the two women Thursday after shooting and injuring their Kenyan driver.

The hijacked vehicle got stuck about 20 miles (30 kilometers) from the Somali border because of rain and bad terrain, said a police official in a position to know but who could not be identified because of agency rules. Police suspect the gunmen may have then forced the women to walk on foot, the official said.

Jehu-Hoyah said the ban on nonessential movement for U.N. staff and their partners from aid groups would remain in place until further notice but that the U.N. was working closely with the Kenyan government to improve security. She said more police had been deployed and extra checkpoints set up.

Security has long been a concern at Dadaab, where representatives from various factions seek to recruit disaffected young male refugees as fighters. Aid workers live in guarded compounds surrounded by high barbed-wire walls, and the U.N. requires its staff to travel in the camps with armed escorts.

Thursday's kidnapping has the potential to severely affect services for a long time to come.

"This incident, in the camp, in the middle of the day, is very worrying," said Alun McDonald, a spokesman for the aid group Oxfam. "Security has become much more of a concern."

All Oxfam staff had been confined to their compound for the day and it is unclear how long the ban on movement will last. The restrictions have so far not significantly affected work providing water to tens of thousands of refugees, McDonald said.

Trips by VIPs who planned to visit the camp to shine the spotlight on the famine as well as trips by journalists have been canceled by the U.N. because of the attack, which follows the September disappearance of a Kenyan driver for CARE during a carjacking.

The agency does not refer to the incident as a kidnapping, said Juliett Otieno, a spokeswoman for the relief agency. She declined to say if there had been contact with the driver or any potential captors. Most of CARE's 250 staffers in Dadaab were confined to the compound Friday, she said.

"The only ones going out are those who perform lifesaving services," she said. "We don't know how long it will last."

The kidnapping is believed to be the first such seizure of foreign aid workers from the camp, although Somalis have kidnapped two other Europeans from Kenya in the past six weeks. The border between Kenya and Somalia is long and porous and both refugees and militants can cross with ease.

On Oct. 1, Somali gunmen took a wheelchair-bound French woman from her home near the resort town of Lamu. Somalis also abducted a British woman from a Kenyan coastal resort in September. Her husband was killed in the attack.

Most of lawless Somalia has been carved up between warlords, pirates and Islamist insurgents battling a weak U.N.-backed government. Western hostages can fetch high ransoms and can spend more than a year in captivity.

"I think the acts of yesterday are appalling, shocking and very very disturbing for all aid workers," said Jehu-Hoyah. "We have colleagues from different NGOs, U.N. agencies and national organizations all working in Dadaab for the benefit of these unfortunate refugees, and to have them attacked like this is very unfortunate."

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Associated Press writer Harold Heckle contributed to this report from Madrid.