Armed militants holding over 350 students and adults hostage in a school in southern Russia on Thursday released 31 women and children.

Russian television showed security personnel carrying babies, one of them wrapped in a blanket and two without shirts, to safety.

As hundreds of anxious relatives waited nearby hoping to see their loved ones freed, President Vladimir Putin, who cancelled his trip to Turkey to deal with the crisis, said that the release of the hostages held in the city of Beslan in North Ossetia is paramount.

"All the actions of our forces... will be devoted to solving this task," he said in a nationally televised address.

"Our main task is to save the life and health of those who have ended up as hostages" since yesterday, Putin said.