Six aid workers have been kidnapped in southern Niger by unknown gunmen, their employers say.
Five of those seized are from Niger and work for medical charity Anbef - the sixth is said to be a Chadian working for Alerte Sante.
One local official blamed the local branch of al-Qaeda, which has seized several Westerners in recent years.
Analysts say the rebel takeover of northern Mali has created a security vacuum in the region.
Niger's government has sent troops and aircraft to search for the aid workers.
They were abducted in the town of Dakoro, where they had been treating malaria and helping malnourished children, the two medical charities said, in a joint statement quoted by Reuters news agency.
Those seized include a doctor, a nurse and a driver with Anbef, local officials say.
Eyewitnesses say the attackers arrived at a guesthouse used by aid workers late on Sunday night in two 4x4 vehicles and then drove off with their hostages towards the desert north.
Local official Idrissa Hassane told the AP news agency: "It seems obvious that these were elements of AQIM [Al-Qaeda in the Islamic Maghreb]... I am hopeful that we will be able to catch them."
Four French hostages are still being held by AQIM two years after being seized in northern Niger.
Niger, one of the world's poorest countries, was hit by a severe drought this year, with the government appealing for international help to end food shortages.
Thousands of people have also fled to Niger after ethnic Tuareg and Islamist rebels seized northern Mali in April.