Iran will punish all those responsible for the accidental shooting down of a Ukrainian passenger plane, President Hassan Rouhani has said in a televised speech, adding that the “tragic event” would be investigated thoroughly.

“It was an unforgivable error … one person cannot be solely responsible for the plane crash,” he said.

“Iranian armed forces admitting their mistake is a good first step … We should assure people that it will not happen again,” he said, adding that his government was “accountable to Iranian and other nations who lost lives in the plane crash”.

The Iranian leader’s comments come after a number of people were  arrested for their role in the missile attack on a Ukraine passenger jet which killed 176 people.

Iran’s judiciary said “extensive investigations have taken place and some individuals are arrested”.

Judiciary spokesman Gholamhossein Esmaili was quoted by Iranian state media, but did not say how many individuals had been detained or name them.

The arrests follow Iranian leaders’ last week assuring the public they would ensure justice was served and the individuals responsible for the “disastrous” mistake would be prosecuted.

Iran’s president Hassan Rouhani on Tuesday called for a special court to be set up to probe the downing of the plane which occurred just after takeoff from Tehran last Wednesday.

The arrests came as European nations issued a joint statement relating to a dispute with Iran over is nuclear ambitions.

France, Britain and Germany  – who are party to a nuclear deal with Iran – have confirmed they have triggered the ‘dispute mechanism’ over Iran’s ongoing nuclear violations.

“We have therefore been left with no choice, given Iran’s actions, but to register today our concerns that Iran is not meeting its commitments under the JCPoA (Iran deal) and to refer this matter to the Joint Commission under the Dispute Resolution Mechanism, as set out in paragraph 36 of the JCPoA,” the three European states said in a joint statement.

However they said they were not joining the USA’s campaign to exert maximum pressure on Tehran.

Plane crash responsibility

Iran, which initially dismissed allegations that a missile had brought down the Ukraine jetliner, later acknowledged that its Revolutionary Guard had shot down the plane by mistake during a period of heightened alert.

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

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.

The admission sparked protests in Iran, with thousands of people taking to the streets over the deaths of the passengers who were mostly Iranian, followed by Canadians.

The shooting has led to one of the greatest public challenges to Iran’s clerical rulers since they came to power in the Islamic Revolution of 1979.

Students have been at the forefront on the fourth day of demonstrations, some met by a violent police crackdown.

Video from inside Iran has shown wounded people being carried, pools of blood on the streets and the sound of gunfire.

Canadian Prime Minister Justin Trudeau told a vigil of mourners he would pursue justice and accountability for the lives of at least 57 Canadians and has also accused the US of stoking tensions in the Middle East.

Ukraine’s foreign minister said five of the countries whose citizens were killed when an airliner was shot down, would meet on Thursday.

“We will meet in person in London to discuss the ways, including legal, (for) how we are following this up,” Vadym Prystaiko said.

-with AAP