Twelve Afghan nationals were killed in an ambush while entering Iran from Afghanistan, an Afghan police border commander in western region said Wednesday, according to dpa. It happened Monday night after a group of Afghan nationals were ambushed by unknown attackers some 25 kilometres inside Iran, Colonel Rahmatullah Safi told Deutsche Presse-Agentur dpa. "We don't know who killed these people," Safi said, adding: "There are two possibilities - that they were either killed by Iranian border police or by enemies of both our countries." He also could not say who the dead Afghans were or why they were crossing the border during the night. "We cannot investigate inside their country, so we since Iran is our friendly neighbour we ask them to investigate the matter and provide us more information," Safi said. Owing to unemployment in Afghanistan, hundreds of thousands of Afghans have crossed the border illegally and currently live in Iran. The Iranian government recently decided to expel over one million Afghans in its country. A further nearly one million Afghans who escaped three decades of war in their homeland have been registered as legal refugees in Iran. The long border is also known as a drug smuggling route to Iran, from where traffickers take illicit drugs to Turkey and western European countries. Afghanistan produces more than 90 per cent of the world's heroin. "No group has the right to kill the smugglers and illegal refugees. If the 12 Afghan men had committed any crime, they should have been arrested, not killed," Safi said.