Bamako - Security forces were searching territory in Mali and Burkina Faso on Thursday for a Colombian nun kidnapped by self-declared jihadists, a Malian security ministry source said.Gloria Cecilia Narvaez Argoti, 56, was seized by armed men in the village of Karangasso close to the Burkina Faso border on Tuesday night."The search goes on. We have men on the ground," the source told AFP. "We have also alerted the authorities in Burkina Faso who are mounting searches from their side because the group headed in the direction of the border," the source added.Two arrests have been made in Mali after four men seized the nun and drove her away in a vehicle belonging to her Franciscan order.In Bogota, the head of the order said the men had said they had "an order to kill" when they grabbed her, adding that she had spent six years in Mali.Edmond Dembele, secretary general of the Episcopal Conference of Mali, said the community was "very worried". "The border areas are vast and often uninhabited, and are opportune for hiding," the priest added.There has not been a claim of responsibility for the kidnapping so far, but attacks in the south of Mali by jihadists, a threat that was once confined to the restive north, have become increasingly common.Last month, Al-Qaeda's affiliate in North Africa released a new proof-of-life video of Swiss missionary Beatrice Stockly, who has been held hostage by the group for more than a year.The Al-Qaeda in the Islamic Maghreb (AQIM) video showed Stockly, who was captured in northern Mali, saying she was in good health.