Human Rights Watch has denounced Iran's hanging of 20 Sunni prisoners in one of its biggest mass executions in years as a "shameful low point in its human rights record".

Shia-majority Iran last week said it had hanged 20 "terrorist" Sunni prisoners on Tuesday convicted of carrying out a string of attacks against civilians and religious leaders in the country's western Kurdish region.

"Iran's mass execution of prisoners on August 2 at Rajai Shahr prison is a shameful low point in its human rights record," Sarah Leah Whitson, Middle East director at HRW, said on Monday.

"With at least 230 executions since January 1, Iran is yet again the regional leader in executions but a laggard in implementing the so far illusory penal code reforms meant to bridge the gap with international standards," she said.

The New York-based rights group said "two lawyers who represented some of the men told [it] that their clients did not get a fair trial and that their due process rights had been violated".

It said rights groups believed the 20 were among 33 Sunni men, including possibly a minor, arrested in 2009 and 2010.

HRW said that recent changes to Iran's penal code required the judiciary to review and annul death sentences of people on that charge "if they had not personally used weapons in committing the crime".

According to rights group Amnesty International, Iran was one of the world's leading executioners in 2015 when it put 977 people to death.

Last week's execution, which was criticized by the European Union and France, came as the EU had reportedly proposed talks with Iran on human rights.

Mohammad Javad Larijani, secretary general of Iran's High Council for Human Rights, said on Wednesday that Foreign Minister Mohammad Javad Zarif and top EU diplomat Federica Mogherini had already held preliminary discussions on the issue.

Larijani said that Tehran was ready to discuss human rights but that "Westerners should not put themselves forward as role models".

In 2013, it hanged 16 Sunnis in the eastern province of Zahedan, eight of whom were members of Sunni militant group Jundallah, which waged a deadly insurgency in southeastern Iran for almost a decade.

PHOTO CAPTION

(R L) Iran's parliament speaker Ali Larijani, Iran's Supreme Leader Ayatollah Ali Khamenei, and Iranian President Hassan Rouhani attend Supreme Leader’s meeting in Tehran, Iran July 6, 2016 (Reuters).

Al-Jazeera