Iranian President Hassan Rouhani has promised to investigate the crash of the Ukrainian Boeing near Tehran and punish those who responsible. The tragedy should not happen again, he said.

“We must complete the investigation to find out all the causes of the disaster and bring to justice those responsible for this inexcusable mistake. It is necessary to take measures to eliminate the weaknesses of the air defense system of Iran so that such a tragedy does not happen again,” Rouhani said in a statement published on the official website of the head of Iran.

On his Twitter page, Rouhani called the crash of the Ukrainian airliner a “great tragedy” and an “unforgivable mistake.” The Boeing-737 “International Airlines of Ukraine” crashed on the morning of January 8 immediately after departure from the airport in Tehran. The plane was heading for Kyiv. It turned out that the airliner was accidentally shot down from the Iranian air defense system, mistaking the aircraft for an enemy target. 167 passengers and 9 crewmembers were killed.