Iranian delegates, who helped secure a nuclear deal with world powers, face death threats from hardline Islamist lawmakers, the chief of Iran's Atomic Energy Agency has claimed. Opposition lawmakers have alleged that the group of negotiators compromised extensively "to serve American interests".

What was planned to be an approval session at the Iranian parliament for the Joint Comprehensive Plan of Action, turned out to be a heated debate instead. Ultraconservative lawmakers repeatedly pointed out the purported fallacies in the deal, to shoot down the arguments made by Ali Akbar Salehi, the chief of the atomic energy organisation.

In his remarks, Salehi, a key negotiator, told the parliament: "Someone has come and tell us 'We will kill you and bury you under cement at the Arak reactor' [sic]." The Arak nuclear reactor was at the nucleus of controversy between the Western world and Iran, which said the facility was used for research activities.

Salehi's speech was frequently interrupted by several lawmakers, who constantly shouted "he is a liar".

"This deal serves Wendy Sherman," said Alireza Zakani, the chief of the panel reviewing the landmark nuclear deal, referring to the top US negotiator. Local reports suggest that this is not the first time Salehi and Foreign Minister Mohammed Javad Zarif -- who was leading the Iranian delegation -- have received such threats. Nonetheless, despite the animated arguments in parliament, the agreement was partially approved with 139 out of 253 MPs present voted in favour of the accord.