Iran denied U.N. reports that it is pressuring Afghan refugees to return home, saying Thursday that the tens of thousands who have gone back to Afghanistan have done so voluntarily. Mohammad Rostami, an Interior Ministry official, said that 176,201 Afghan refugees have already gone back to Afghanistan, "all of them voluntarily and without any pressure," according to the official Islamic Republic News Agency. On Sunday, the U.N. High Commissioner for Refugees complained that Iranian authorities are pressuring Afghan refugees to leave their longtime homes in Iran and return to Afghanistan. The agency said that such induced returns violate an agreement signed by the Iranian and Afghan governments and the UNHCR in April. It said the number of Afghan refugees crossing the border from Iran rose from an average of 6,500 weekly in July to 10,000 in the first week of August. Rostami said the increase "was due to the (refugees') interest in voluntary repatriation, given better security conditions in Afghanistan," IRNA reported. Rostami put the number of Afghan refugees in Iran at more than 2 million while the UNHCR puts it at 1.4 million. Iran has set a deadline requiring Afghan refugees who have not registered for repatriation to return home or face arrest. On Sunday, it extended that deadline to Aug. 27. IRNA said Afghan refugees were now required to present passports and valid visas to enter Iran. Some returnees said Iranian authorities had refused to register their children for the new school year, and were informing refugees that if they did not return to Afghanistan immediately they would not be eligible for U.N. financial and other assistance, Maki Shinohara, UNHCR spokeswoman in Kabul said Sunday. This report of a U.N. deadline is untrue, Shinohara said. The UNHCR embarked on a huge repatriation program for the more than 4 million Afghan refugees outside the country's borders in March, three months after a U.S.-led military campaign brought down the Taliban government and generally restored peace to Afghanistan. The agency stresses the voluntary nature of returns, by refugees who feel confident they can resettle in their former villages or elsewhere. It points out that forced returns, to places where security or economic support are inadequate, will often backfire and lead returnees to leave the country again.