A former Iranian ambassador to the United Nations on Thursday accused Tehran of promoting sectarianism and seeking to destabilize the Middle East through subverting governments and funding Shia militancy.

Mansour Farhang, who was the Islamic republic's first ambassador to the UN, said in an opinion letter published on The New York Times' website that Iranian officials' criticism of Saudi Arabia for sectarianism and human rights record is "a case of the pot calling the kettle black".

"Iran is a notorious violator of human rights and promoter of sectarianism. In 2015, nearly 700 at least were executed in Iran," Farhang wrote in response to a Jan. 10 op-ed penned by the country's Foreign Minister Javad Zarif.

"Mr. Zarif calls Saudi Arabia's execution method barbaric, but he serves a regime that orders lashing of teenage rape victims before executing them", Farhang said.

In his article published in the same newspaper, Zarif harshly criticized what he called "Saudi Arabia's reckless extremism" and "barbarism".

He said perpetrators of many terrorist acts from 9/11 attacks to San Bernardino shootings, as well as members of terrorist groups like al Qaeda and the Nusra Front, "have been either Saudi nationals or brainwashed by petrodollar-financed demagogues".

"The barbarism is clear. At home, state executioners sever heads with swords, as in the recent execution of 47 prisoners in one day, including Sheikh Nimr al-Nimr", wrote Zarif.

Friction between the regional rivals skyrocketed earlier this month when Saudi Arabia executed al-Nimr and 46 others, that led to protests in Iran and the storming of the Saudi embassy in Tehran.

Farhang, who says he left Iran as a dissident in 1981, said the Iranian and Saudi regimes are "corrupt and intolerant".

While Saudi Arabia "rules a country that wants to preserve the status quo in the Middle East", Iran's leaders "want to export their revolution to Arab countries and thus seek to destabilize the region through subversion and propaganda as well as military and economic assistance to Shiite militias in Iraq, Yemen, Syria and Lebanon," he alleged.