The head of security at Azerbaijan’s embassy in Tehran was killed early on the morning of January 27 when a gunman stormed a guard post at the building, Azerbaijan’s foreign ministry said in an official statement. Two security guards were injured, but their condition was described as stable.

There was an immediate disagreement between Iranian and Azerbaijani officials over what appears to have occurred at around 08:00 Tehran time (04:30 UTC).

"The attacker broke through the guard post, killing the head of security with a Kalashnikov assault rifle. Two security guards of the embassy were also injured while preventing the attack," the Azerbaijani foreign ministry said, identifying the killed employee as Orkhan Asgarov.

The alleged attacker, Yasin Huseynzadeh, an Iranian citizen in his 50s, was detained, according to the Tehran Police chief, Sardar Hossein Rahimi. Rahimi said Huseynzadeh entered the embassy with two young children and that the initial investigation showed the incident was personally motivated, with the gunman having family problems.

However, the Azerbaijani side was not satisfied with the Iranian explanation. Azerbaijani media released security camera footage of the moment of the attack, and it does not show any children brought into the embassy.

"We do not think that the attack on the Azerbaijani embassy in Iran was carried out on personal grounds," a spokesman at the Azerbajani foreign ministry, Aykhan Hajizadeh, told TRT Haber.

Relations between Iran and Azerbaijan have soured in the past couple of years, with military drills held by each side near the Iranian-Azerbaijani border becoming points of contention. Tehran has become concerned at the changing dynamics in the neighbouring South Caucasus since Azerbaijan, closely allied with fellow Turkic-speaking nation Turkey, gained territory as a consequence of its victory in its second war with Armenia over the Nagorno-Karabakh territory in 2020.

Iran also recently watched with consternation as Azerbaijan went ahead and opened an embassy in Israel, Iran’s arch-enemy. Israel, like Turkey, sells arms to Azerbaijan.

Another difficulty in relations between Tehran and Baku is that Iran is home to millions of ethnic Azerbaijanis. Iran is suspicious of any efforts that it sees as adding to Azerbaijani separatist sentiments in northern Iranian territories, where the vast majority of the ethnic Azerbaijanis live.

Turkish Foreign Minister Mevlut Cavusoglu condemned the “treacherous attack” on Azerbaijan’s Tehran mission on Twitter. “Azerbaijan is never alone,” he said, sending his condolences to the relatives of the victim and wishing a speedy recovery to the injured.

Shortly after on Twitter, Azerbaijan's President Ilham Aliyev described the attack as "an act of terrorism" and demanded swift punishment.

"I firmly condemn the act of terrorism carried out at the embassy of Azerbaijan in Tehran," he said.

Around lunchtime in Tehran, Mizan, a news agency affiliated with Iran's judiciary, quoted Iranian prosecutor Mohammad Shahriari as saying the gunman’s wife disappeared in April last year after a visit to the Azerbaijani embassy. Shahriari added that the suspect said he believed that at the time of the attack, his wife was still in the embassy.