Hours after a suspicious explosion in northern Tehran in the early hours of Saturday, Iranian media reported a cyberattack on the computer systems of the ministry of transportation and urbanization which forced the ministry's portal to shut down.

Social media users have posted a screenshot taken from the ministry staff computers which showed a message from the hackers taking responsibility for Saturday's attack as well as an attack on Friday on the Islamic Republic of Iran Railways (Raja) which caused massive disruption in train schedules.

The attack on the railways caused delays and cancellations of hundreds of scheduled trains across the country and shut down systems for booking tickets and other services. Iranian media have described the situation at train stations as "unprecedently chaotic".

Twitterati have reported that after the attack boards at train stations showed all scheduled trips as canceled and a text message posted on the boards provided a telephone number for enquiries which turned out to be the number of the Supreme Leader Ali Khamenei's office forcing the authorities to turn off the boards.

Sadegh Sokri, head of Public Relations of the Railways, Saturday denied a cyberattack and said there had only been a "disruption in cargo transport".

Authorities say the explosion in northern Tehran happened at Mellat and caused no damages. The Park is located near sensitive buildings including the headquarters of the state broadcaster (IRIB), the Industrial Development and Renovation Organization (IDRO) which is involved in Iran's nuclear, missile and space programs, as well as the Revolutionary Guards' Sarallah headquarters and its Madineh (Medina) underground facilities.

Officials have not offered any explanation about the explosion and claim no damages have been observed anywhere near where the sound of the explosion was reported. Social media users claim that the sound and tremor of the explosion were strongly felt both in the north and west of the capital.

Zeytoon, a reformist news website, said Saturday afternoon that "unofficial sources" claim the explosion took place at Shahid Avini building of the IRIB. According to Zeytoon, the building is located where Sarallah Headquarters and Madina underground facilities of the Revolutionary Guards are connected to each other and the emergency exit of Sarallah is located.

In an Instagram post on Saturday, Minister of telecommunications, Mohammad-Javad Azari-Jahromi has warned about possible cyberattacks similar to some attacks in 2018 when servers were targeted with ransomware through portal admin systems. Azari-Jahromi said new cyberattacks attempts of this type have been detected recently.

In July 2020 a series of mysterious explosions and fires happened at sensitive military and civilian sites in Iran, including an explosion at Natanz enrichment facilities near Qom which Iran says Israel is responsible for.

More recently, there have been huge blazes at a chemicals plant near Qom in May and Tehran's oil refinery and a possible explosion at Iran Navy's largest ship in the Gulf of Oman, both on June 2.