Iranian state media said earlier that the internal computer system of the municipality of Tehran was targeted in a “deliberate” shutdown Thursday in the latest apparent cyber attack in the country.

The People’s Mujahedin of Iran (MEK), which is outlawed in Iran, said in a statement that their operatives inside the country had carried out the attack “in a major operation, planned months in advance.”

It said the hacking attack on the Tehran municipality websites saw images appear of MEK leader Massoud Rajavi, who has not been seen in public for years, and his wife Maryam Rajavi, as well as slogans against supreme leader Ayatollah Ali Khamenei.