Iran's judiciary says arrests have been made over the shooting down of a Ukrainian plane that killed all 176 people on board.

"Extensive investigations have taken place and some individuals are arrested," the judiciary spokesman, Gholamhossein Esmaili, said on Tuesday.

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He was quoted by Iranian state media but did not say how many individuals have been detained or name them.

Iran's president on Tuesday called for a special court to be set up to probe the downing of the plane last week just after takeoff from Tehran.

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Iran, which initially dismissed allegations that a missile had brought down the jetliner, acknowledged that its Revolutionary Guard had shot down the plane by mistake.

Rouhani called the incident "a painful and unforgivable" mistake and promised that his administration would pursue the case "by all means."

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Iran shot down the plane when it was bracing for possible US retaliation for a ballistic missile attack on two military bases housing US troops in Iraq. No one was hurt in that attack, which was carried out to avenge the stunning killing of Revolutionary Guard General Qassem Soleimani in an American airstrike in Baghdad.