The International Campaign for Human Rights in Iran said the 10 prisoners were executed at Vakilabad prison in Mashhad in early March without their families or lawyers being informed.
In a report to the UN Human Rights Council in Geneva on March 14, Secretary-General Ban Ki-moon voiced concern about the human rights situation in Iran, including the executions of drug traffickers.
"In July 2010, a large number of prisoners were reportedly executed at one time in Mashhad prison," Ban's report said.
"When OHCHR [Office of the High Commissioner for Human Rights] staff sought further information from Iranian counterparts during a visit to Tehran in December 2010, they confirmed that 60 persons had been executed in Mashhad in pending cases mostly linked to drug trafficking."
Hadi Ghaemi, the director of the New York-based group, told RFE/RL's Radio Farda, "The significant point regarding these  executions is that they have been documented in the latest report of the Secretary-General of the UN."
But he added, “Despite the concerns of the Secretary-General, these executions were continued on March 2, when 10 more prisoners were executed."
Ghaemi said his group understands that the latest group of executed prisoners included Afghans and Africans.
He said that such prisoners typically are unaware of the date of their execution until the last moment.