Five African aid workers who were abducted in Niger in mid-October have been freed, while a sixth has died after being shot by the al-Qaeda-linked kidnappers, the workers and their employers said.
Five Niger nationals "were freed today and are currently in Niger", while their colleague Aime Soulembaye from Chad has "died from his wounds", Niger's Befen and Chad's Alerte-Sante aid agencies said in a statement.
The groups did not say how the aid workers were freed.
Chad's foreign ministry issued a statement confirming the death of their countryman.
"Chad strongly condemns this kidnapping which has led to the death of a totally innocent Chadian national who was in Niger to help needy people, and we hold responsible the kidnappers who we want to see answer for their acts," the ministry statement said.
One of the hostages said the kidnapping was carried out by the armed Islamist group Movement for Oneness and Jihad in West Africa (MUJAO), a group among several backed by al-Qaeda that have seized control of the north in neighbouring Mali.
"We were kidnapped by people from MUJAO. They thought there was a white person with us," the freed hostage said by phone from the Niger-Mali border.
"We were released not far from the border, and we walked," he added.
"Our Chadian friend died from his wounds. He was in a very bad condition."
Niger President Mahamadou Issoufou met the freed aid workers at his residence in Niamey, after which he told reporters: "We are happy that these five returned safe and sound," while regretting the death of the Chadian hostage.
His Interior Minister Abou Labo meanwhile denied that any ransom had been paid.
Issaley Aboulkader, a former hostage who works for an aid group, said the hostages were held in "precarious" conditions and were unable to bathe for nearly three weeks. He described the hostage-takers as "black Arabs" and said some spoke English.
Another, a veterinarian working for another aid group, said the hostage-takers "did not mistreat us, neither physically nor mentally".
He added that they had buried Soulembaye "out in the bush" the day after the October 14 kidnapping in southeastern Niger.
The aid groups said Soulembaye had been shot by the kidnappers during the abduction.
His death is "an unjustifiable and incomprehensible tragedy for the humanitarian world", they said.
Security sources in Niger and Mali confirmed the five hostages had been freed at the two countries' border.
The kidnappers had been targeting an Italian anthropologist who was working for aid group Doctors Without Borders (MSF), a local official in the Niger town of Dakoro said shortly after the abduction.
Mali was plunged into chaos by a March 22 coup that ousted president Amadou Toumani Toure, creating a power vacuum that enabled several al-Qaeda-linked groups including MUJAO to seize control of the country's vast desert north.