Pakistan protested to India on Wednesday after the son of a Pakistani embassy worker in India was said to have been kidnapped and bizarrely photographed with three corpses before being released.
Nineteen-year-old Roshan Ali was abducted and harassed by unidentified attackers in New Delhi late on Tuesday, foreign ministry said in a statement.
Pakistan summoned India's Acting High Commissioner in Islamabad to the foreign office and a "strong protest was lodged with him condemning the premeditated and cowardly act", the ministry added.
While he was detained at an unknown location, the teenager's hands were "smeared with the fresh blood of three dead bodies lying in the room," the statement said.
"He was forced to hold a large bloodstained knife in his hands and to stand next to the dead bodies. He was then photographed in various poses with the dead bodies," it added.
Ali's attackers stuffed a threatening hand-written note addressed to his father into his pocket and then took all his belongings before throwing him out of a vehicle after midnight, the statement said.
The note was addressed to his father and said that the teenager "should be taken out of Delhi within five days because the abductors had photographs that could send him to the gallows," the ministry added.
Foreign ministry had asked India to carry out an investigation and to ensure that "deplorable" incidents of its kind did not happen again.
It said the Indian diplomat had "expressed regrets over the unfortunate incident and assured that an investigation would be undertaken and the results shared with Pakistan."
In New Delhi, Indian foreign ministry spokesman Navtej Sarna said the matter was being investigated.
"The alleged abduction of a dependent of an official of the Pakistan High Commission has been brought to our attention. The matter is being investigated," Sarna said in a brief statement.