Aid workers have travelled to a remote Niger rebel base, where 72 soldiers are being held, to deliver drugs and other humanitarian assistance.
Many Tuaregs say they are marginalised by the government
Some of those captured were injured when Tuareg rebels attacked their military base on Friday.
The International Committee of the Red Cross team has travelled to Tizerzet in the Sahara desert, some 400km north of the nearest town, Agadez.
A BBC reporter says locals are shocked that rebels captured so many troops.
The BBC's Idy Baraou in Agadez says he saw four truckloads of aid, while ICRC officials said they were taking more.
"There are seriously wounded people who need to be evacuated," Niger Movement for Justice (MNJ) leader Agaly Alambo told the AFP news agency.
Our reporter says it was Niger's biggest rebel attack since a rebellion first began in 1991.
That uprising ended with a 1995 peace deal but earlier this year the MNJ took up arms, saying the terms of that deal were not being implemented.
In April, the rebels, who say Tuaregs are marginalised by the government, attacked a uranium mine in northern Niger.
The north of Niger is rich in uranium and the country is one of the world's top five uranium producers.