The United Nations has scaled back its aid operation at Kenya's massive Dadaab refugee camp near the Somalia border, after two female aid workers were kidnapped.

U.N. officials say all non-lifesaving activities have been put on hold until the security situation improves. Aid groups are continuing to provide food, water and medical services.

Nearly 500,000 people are staying at the world's largest refugee camp, where thousands of Somalis have fled in recent months to escape drought, famine and insecurity in their own country.

Kenyan police suspect the Somalia-based militant group al-Shabab abducted the two European aid workers on Thursday, and officials believe the gunmen tried to take the women into Somali territory.

The medical aid group Doctors Without Borders has confirmed two Spanish staff members were abducted at the camp and says it is doing everything possible to ensure their safe return.

So far, there have been no reports of ransom or other demands from the kidnappers.

A senior official with al-Shabab told the French news agency that the al-Qaida-linked insurgent group is not behind the abductions.

A driver working with the aid workers was shot during the abduction and left behind. An official for Doctors Without Borders told VOA he is in stable condition.

It is the third kidnapping of foreigners near the Somalia-Kenya border in the past month.

A British tourist and a French woman were recently abducted at Kenyan resorts. Both of those women are being held captive in Somalia.