The Azerbaijani State Security Service has arrested five people over the attempted killing of MP Fazil Mustafa, and has said the ringleader was working for Iran's secret services.

The discovery of the alleged plot threatens to plunge Iranian-Azerbaijan relations to a new low. Azerbaijan has accused Iran of not properly investigating an attack on its embassy in Tehran in January, and conducting threatening military exercises close to its border. Iran has been angered by Azerbaijan's growing links with its enemy, Israel, and by its demands for territory in Armenia close to its border.

According to preliminary information from the authorities, the organiser of the attack was named as Sarijanov Azer, who was better known as "Hajji Azer". The Salyan-born, 47-year-old cleric visited Iran 11 times between 2010 and 2019. He lived in Qom city of Iran from 1993-2002, receiving his religious education. According to the SSS, after returning to Azerbaijan, he established business activities in the country under the name of charity with the financial support of Iran's special services. During the following period, he visited Iran many times. Authorities accuse him of financial and organisational work on orders received from Iran's special services. 

The would-be assassin was named as Shirinov Sabuhi, a 37-year-old citizen. According to Azeri authorities, he visited Iran 15 times between 2017-2022. SSS accuse him of being in cooperation with Iran's special services and undergoing combat training. Three more people were arrested alongside him as being members of the same group and aiding him in this attack.

The attack is regarded as a "terrorist attack" by the Azerbaijani state and it officially accused the neighbouring country of sponsoring terrorism. On April 3, the Azerbaijani Ministry of Foreign Affairs summoned Iranian Ambassador Seyyid Abbas Mousavi to discuss concerns regarding "the dissemination of false and biased information about Azerbaijan" in Iranian media. The meeting came after the Azerbaijani Foreign Ministry received a note from the Iranian Embassy and subsequently issued a response note.

Earlier, in a special report on the operations of the State Security Service, which was broadcast by public television on March 27, "a plan to assassinate a well-known public figure" was mentioned. It was claimed in the programme that citizens called Faig Zeynalov, Etibar Mammadzade and Huseyn Huseynzade were spying for Iran in Azerbaijan on the instructions of a person named Ruhulla Akhundzade. The accused person, Zeynalov, said in his statement that there was a plan to first follow the unnamed "public figure" in Baku, and then injure him with a knife or a firearm. According to him, the goal was to "give that person an eyeful". The name of the public figure mentioned in the material has not been disclosed. However, there are similarities between the "method of punishing a public figure" and the details of the assassination of MP Fazil Mustafa, according to Toplum TV.

A wave of arrests in Azerbaijan started about a month and a half ago after an armed attack on the Azerbaijani embassy in Iran. At that time, the tension between the two countries was followed by the arrest of people known as "believers" in Azerbaijan on drug charges in late January-early February. Even at that time, the Ministry of Internal Affairs announced that more than 45 "Iranian spies" were detained, but no detailed information was given. Currently, according to unofficial sources and claims on social media, more than 400 people have been detained, however,  Spokesman of the Minister of Internal Affairs Elshad Hajiyev Toplum TV.

According to lawyer Samed Rahimli, the Tartar case and former criminal cases by the now-defunct National Security Ministry show that Azerbaijan is incapable of conducting evidence-based criminal cases even in matters where it may be right. "The state of Azerbaijan is institutionally unable to conduct an investigation. Taking into account the inability of the Azerbaijani state to conduct an investigation, it is necessary to be sceptical from the beginning of the presentation that these people are spies of this and that state," he said.

MP Bahruz Maharramov, while acknowledging that investigation wasn't at the end yet, claimed that Iran didn't just attack Fazil Mustafa, but the "statehood of Azerbaijan" in his interview to the VOA Azerbaijani service.