There's been a second attack within two days in northern Mali on a military convoy by Tuareg rebels.
Many Tuareg feel they have not benefited from uranium wealth
Reports from the Kidal region say insurgents attacked three army vehicles close to the border with Algeria, abducting all of their occupants.
The number of missing soldiers is unclear.
On Monday, the authorities in Mali confirmed reports that 15 soldiers had been seized close to the border with Niger; their whereabouts are unknown.
The main Tuareg movement in Mali say it is abiding by last year's political agreement with the government that ended its insurgency conflict.
But last week, a Tuareg splinter group in Mali announced it had formed an alliance with Tuareg rebels in neighbouring Niger, who have begun a new military offensive this year against the Niger government.
The governments of Mali and Niger have said they will work together against the rebels who have demanded better development and a share of Niger's mineral wealth.
The soldiers snatched in Tedjerete in Mali were protecting agricultural technicians working to halt a locust infestation.
Since February the Tuareg rebels, known as the Niger Movement For Justice, have killed over 40 soldiers.
The attacks have been in the remote north of Niger which is rich in uranium.
In addition to demands for more development the rebels have also called for a fairer share of the mining revenue.
Niger's President Mamadou Tandja has vowed to fight rather than negotiate and declared a state of alert in the region giving extra powers to the military.
Over the weekend, a delegation headed by Niger's prime minister travelled to Sudan and Libya to seek help in ending the insurgency.