Iran has yet to hand over vital documents relating to its military's shooting down of a Ukrainian passenger plane in 2020 that killed 176 people, the Foreign Ministry in Kiev said on Monday.
Iran had invited Ukraine's ambassador in Tehran to attend a military trial that began on Monday, after Iran's own investigation.
Ukraine expressed "gratitude" for the invitation before warning that Iran was not complying "with its obligations under international law and to provide requested information to the Ukrainian authorities".
The ambassador will not attend the trial, the ministry said.
"As of today, the requests for international legal assistance in criminal proceedings, sent by the Ukrainian side to the competent authorities of the Islamic Republic of Iran, have not been fully complied with, the requested documents and information have not been provided by the Iranian side," the ministry said on its website.
The Irna news agency said 10 military personnel – suspects from “various ranks” – were present at Sunday's hearing, after an Iranian report into the disaster that was completed in March.
That report was condemned by Ukraine's Foreign Minister Dmytro Kuleba as "a collection of manipulations, the goal of which is not to establish the truth but to whitewash the Islamic Republic of Iran".
Families of victims and their lawyers attended Monday's session, representing 103 legal complaints over the shooting down of Ukraine International Airlines flight PS752.
The report quoted the unidentified judge as saying he hoped the court would issue a “precise, quick and serious” verdict, based on a “reasonable, fair, transparent, clear-cut and strong” procedure.
The court heard statements by lawyers of victims’ families and the report said the next session would be announced after further investigations by the prosecutor.
The report did not identify the suspects. Sunday’s session was the first hearing since the incident nearly 22 months ago.
In April, a prosecutor said 10 officials have been indicted over the case. That came a month after Iran faced international criticism for releasing a final report that blamed human error without identifying the persons responsible.
In January 2020, after three days of denial in the face of mounting evidence, Iran eventually acknowledged that its paramilitary Islamic Revolutionary Guard Corps mistakenly downed the Ukrainian plane with two surface-to-air missiles.
In preliminary reports in 2020, Iranian authorities blamed an air defence operator who they said mistook the Boeing 737-800 for an American cruise missile.
It happened on the same day Iran launched a ballistic missile attack on US troops in Iraq in retaliation for an American drone strike that killed a leading Iranian general.
But instead of blaming a single air defence operator, a panel of Canadian experts who compiled a government-commissioned report into the disaster in June last year said that failures had been systemic.
With 10 people on trial from various ranks, Iran now appears to be taking this view.
The report by aviation analysts said that Iran's air defences suffered a "command and control failure," — with better co-ordination, the missile battery which downed the plane would have 'known' in advance that a civilian airliner was at risk.
"Iran’s account refuses to analyse the full range of deficiencies in the military sector that played a major role in the downing. Iran’s military command and control over the SAM unit failed. If it were functioning properly, the shoot-down would not have occurred," the report said.
Later, IRGC officials publicly apologised for the incident. But the hesitancy of Iran to elaborate on what happened perhaps shows the power the force wields.