The first bodies of Iranian pilgrims killed in a stampede at the annual hajj arrived home Saturday -- nine days after the tragedy which sparked anger and criticism of Saudi Arabia.
President Hassan Rouhani and other top officials attended a repatriation ceremony for the 104 pilgrims, who were among at least 464 Iranians killed in the September 24 crush.
"If it were proved that some (authorities) were guilty in this accident, we will not forgive" the loss of our loved ones, said a sombre Rouhani said, flanked by the heads of the judiciary and parliament as well as the chief of staff of supreme leader Ayatollah Ali Khamenei's office.
"Our language in this accident was one of brotherhood and respect and the language of diplomacy was used when necessary," said Rouhani.
"If needed, the language of authority will also be used."
Rouhani called for a "fact-finding commission" into the disaster that Iranian leaders have blamed on Saudi "mismanagement and incompetence".
"All Islamic countries must learn why this tragedy happened," he said.
Saudi authorities have yet to provide a breakdown of the nationalities of the 769 Muslim pilgrims they say were killed, but many countries have announced the deaths of citizens.
Tallies of the dead from foreign officials and media from 24 countries put the toll at 1,036, well in excess of the Saudi figure.
With many more pilgrims still listed as missing, Iranian officials say the real toll is between 2,000 and 4,000.