A group claiming to be holding an American UN official in Pakistan threatened to kill him in 48 hours if the government does not free more than 1,100 prisoners, a report said.
John Solecki, head of the UN refugee agency (UNHCR) in the southwestern province of Baluchistan, was snatched at gunpoint from the city of Quetta while travelling to work on February 2.
His driver was killed during the abduction.
A spokesman for the Baluchistan Liberation United Front (BLUF) called the private Online news agency in Quetta late on Monday to say the United Nations had to play its role in fulfilling their demands within 48 hours.
BLUF has only been communicating with Online.
"If anything happened to John Solecki, who is a heart patient, then we will not be responsible," Online quoted spokesman Shahak Baloch as saying.
"We have given our demands to the United Nations that 1,109 of our people and 141 women prisoners should be recovered, but UN officials have not shown seriousness," Baloch said.
"His condition is deteriorating, we are providing him every possible medical treatment, but it is making no difference," Baloch said.