Saudi Arabian government websites have been targeted by hackers, forcing several offline for more than 24 hours. Reports in Iran claim that the cyberattack was a response to the execution of leading Shia cleric Sheikh Nimr Baqir al-Nimr in Saudi Arabia, while members of the hacktivist collective Anonymous have taken credit for the shut downs.

Hackers conducted a massive distributed denial of service (DDoS) attack against the Saudi Arabian Ministry of Defence website, which was still down at the time of publication. Such attacks work by flooding the target server with web traffic, usually stemming from a botnet, in order to overload it and force it offline.

Other targets included the Saudi Ministry of Finances, the Saudi Cusoms Service, the General Passports Service and the Saudi Ombudsman's Office.

The Saudi Arabian Ministry of Defence did not respond immediately to a request for comment from IBTimes UK.

The execution of Nimr, an outspoken critic of the Sunni kingdom, led Iran's supreme leader Ayatollah Ali Khamenei to say Saudi Arabia faced "divine vengeance" for Nimr's "unjustly spilled blood". The decision to execute Nimr was also condemned by the US, UN and EU.

Iran's Fars News Agency reported that the DDoS attack was carried out by a group called "Brave Youth Against Religious and Holy Taboos" (Google Translate).

In a statement obtained by Fars, the hackers said: "We will continue defending the religious sanctities and also targeting the enemies and oppressors involved in the killing of the freedom-seekers and revolutionaries."

Several Twitter accounts associated with Anonymous have taken credit for the attack, referring to it as part of Operation Nimr (#OpNimr). The amorphous group also targeted Saudi government websites in September in response to the state's decision to behead and crucify 21-year-old Ali Mohammed al-Nimr, the nephew of Sheikh al-Nimr. A date for his execution is yet to be set.