Araqchi said Saturday the funds would be deposited in an Iranian bank account in Switzerland.
"As far as I know, all necessary measures have been taken and transfers are under way," he told the Islamic Republic News Agency.
The Iranian Students News Agency reported the first transfer totals $550 million.
Iran, under the terms of a six-month nuclear agreement reached with Western powers in November, secured access to funds frozen by international sanctions. In return, Iran agreed to suspend some of its nuclear research activity.
The Iranian currency, the rial, collapsed in 2012 under sanctions pressure.
Under new Iranian President Hassan Rouhani, the government said it's expecting major new investments in its energy sector.
Iranian oil officials said they would announce a new framework governing oil contracts at a London energy conference in July.