Iran's Acting President Mohammad Mokhber paid tribute to his predecessor but said the business of government must continue as he addressed the country’s new parliament in Tehran on Monday.

It marked his first public speech since the helicopter crash that killed Iranian President Ebrahim Raisi, Foreign Minister Hossein Amir-Abdollahian and seven others.

Mokhber stressed that the state's institutions would continue working without 'any delay', despite mourning for those killed in the helicopter crash.

"Even though the entire nation of Iran was mourning for these people, the Assembly of Experts and the Islamic Consultative parliament started working on time, and according to the Supreme Leader, who said at the first moments of the incident, the affairs of the country's administration should not be interrupted, and no plan should face any delay, this was realised," Mohammad Mokhber said.

The twelfth term of Iran's parliament officially started with the 290 elected duties and a large number of national and military officials, ambassadors, and foreign guests.

Mokber also went on to say that Raisi has shifted the 'world's power equations', adding that the unipolar system in the world had come to an end.

"Just a few days ago, one of the major leaders of the world said that Mr. Raisi has shifted the world's power equations in with his performance. He is right, now, the time when people sat in one place and decided for the world and all (countries) were obliged to comply with it, is no longer true," he added.

Interim speaker Alaeddin Boroujerdi also addressed the deputies, saying that the aim of the government was 'stability' but it would also take strong action to protect itself.

"The policy of the Islamic Republic of Iran in the region and the world is not to seek war, but to establish stable security and co-operation with the countries of the region, although it will act decisively against any aggression and coercion," he said.

The 63-year-old Iranian president, his foreign minister and others were killed when their helicopter came down in the mountains in northern Iran’s East Azerbaijan province in heavy fog last weekend.

Iran’s Supreme Leader Ali Khamenei declared five days of national mourning. First Vice President Mohammad Mokhber will serve as acting president for an interim period, with elections scheduled on June 28. Deputy Foreign Minister Ali Bagheri Kani is acting foreign minister.

Messages of condolence arrived from the leaders of Russia, India, Pakistan, Iraq, Syria, Egypt and others. Raisi, a conservative cleric seen as close to Ayatollah Khamenei, was elected in 2021.