"Despite the success of military intervention in Mali, there remains a very real threat of kidnap to Westerners in areas of the Sahel and North Africa," Robertson said in a statement Friday.
Several Westerners have been abducted in the region by members of al-Qaida in the Islamic Maghreb, the North African branch of al-Qaida, official say.
Last month, Radio France Internationale confirmed two of its journalists, Ghislaine Dupont and Claude Verlon, were killed by AQIM while reporting from Mali. AQIM said it carried out the action "to punish France for her new crusade" in Mali.
In January, the Malian government asked for military support from former colonial power France to tackle an al-Qaida threat.
Robertson said groups like AQIM rely on kidnap for ransom to finance their terrorist activity. The minister said his government rejects ransom payments.
"It is a very tough policy to follow, but we believe that this is the only way to prevent further kidnappings," he said.
Astronomers offer more expansive view of universe
Beautician charged with giving client fatal silicone butt injection