Mehmanparast was quoted by the Fars news agency as saying that diplomatic efforts by Tehran with Islamabad had failed to produce results.
"Finally, the [Iranian] intelligence agents themselves freed our diplomat," he was quoted as saying. "The release of the diplomat shows the strength of Iran's security [forces]."
Moslehi alleged that Attarzadeh's abductors were supported by Israeli and US intelligence services.
"Mossad and American intelligence services were supporting the group who abducted the Iranian diplomat," he said. "Mossad and American intelligence are stunned by this rescue operation."
The envoy's release comes after Iranian agents in February captured Abdolmalek Rigi, Tehran's most wanted Sunni fighter, who according to officials in Iran lived in Pakistan from where he launched attacks on the Islamic Republic.
Rigi, the head of the rebel Jundallah (Soldiers of God) group, was seized after Iranian warplanes reportedly forced a flight from Dubai to Kyrgyzstan to land in Iran.
Iran touted his arrest as a major success of its intelligence agencies and a blow to the United States and Britain.
Soon after his arrest, Iranian state television aired a confession by Rigi in which he claimed that he was supported by the United States and had been promised a base along the border with Afghanistan near Iran.
His group says it is fighting for the rights of Sunni Baluchis of the province in mostly Shia Iran.