Nine others were injured in the attack in the up-market University Town area that houses many important installations, including offices of several UN agencies.
Police said a suspicious vehicle stopped close to a security check post near the Iranian Consulate. A man emerged from the car, walked up to the post and blew himself up.
The blast killed two Frontier Corps personnel in the check post.
His spokesman called up newspapers and news agencies in Peshawar to accept responsibility for the attack on the Iranian Consulate. "We will conduct similar attacks against Shias in the coming days," he said.
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Khyber-Pakhtunkhwa Health Minister Shaukat Yousafzai told reporters that the Iranian Consulate was the apparent target of the attack.
Mast Gul alias Haroon Khan, who was involved in the infamous siege of Charar-e-Sharief in 1995, had also claimed a suicide attack on a hotel in a Shia-dominated area of Peshawar that killed nine persons earlier this month.