Iran's Supreme Leader Ayatollah Ali Khamenei has said Saudi Arabia should apologize for a deadly stampede at the annual hajj pilgrimage.
Saudi officials say 769 people were killed and more than 900 injured in the September 24 crush outside Mecca -- the deadliest incident to hit the hajj in 25 years.
Tehran says at least 144 Iranians are among the dead, and that more than 320 others remain unaccounted for.
Khamenei was quoted as saying on September 27, "This issue will not be forgotten and the nations will pursue it seriously."
"Instead of accusing this and that, the Saudis should accept the responsibility and apologize to the Muslims and the victims' families," he also said in comments reported by the official IRNA news agency.
"The Islamic world has a lot of questions. The death of more than 1,000 people is not a small issue," the supreme leader added, citing claims by Iranian officials of a higher death toll.
The comments come a day after a speech by Iranian President Hassan Rohani at the UN in which he called for an investigation into the "heart-rending" stampede.
Meanwhile, Iranian state prosecutor Ebrahim Raisi said Iran would seek the trial of the Saudi royal family over its "crime" against the pilgrims in "international courts and organizations."
Iranian Culture Minister Ali Janati is to head a delegation to Saudi Arabia to oversee the repatriation of those killed and follow up on the cases of those still missing and injured, but IRNA reported that the delegation had still not received visas.
Saudi Arabia has accused the Iranians of playing politics with a tragedy.
"I would hope that the Iranian leaders would be more sensible and more thoughtful with regards to those who perished in this tragedy and wait until we see the results of the investigation," Foreign Minister Adel al-Jubeir said on September 27.
Saudi Arabia's most senior cleric, Grand Mufti Sheikh Abdul Aziz bin-Abdullah al-Sheikh, defended the authorities, saying the stampede was "beyond human control."
King Salman has ordered a safety review into the disaster, in which 18 Pakistanis were also killed.
The religious pilgrimage entered its final day on September 26.
With reporting by AFP and Reuters