The Iranian Foreign Ministry has condemned a terrorist attack on a mosque in the Shia-populated region of al-Ahsa, in Saudi Arabia's Eastern Province, Press TV reported.
Hossein Jaberi Ansari, the ministry spokesman, said on Friday that the repetition of terrorist attacks on mosques and religious centers in eastern Saudi Arabia indicates worrying security situation in this region.
It also showed the negligence of Saudi security forces in fulfilling their responsibilities to provide security for people against attacks by terrorists, he added.
At least four people were killed and 18 wounded in the attacks, which targeted the Imam Reza Mosque in the town of Mahasen in al-Ahsa on Friday.
There was no early claim of responsibility for the attack but it resembled previous assaults by Daesh terrorist group.
Towns and cities in the Shia-dominated Eastern Province have been the site of peaceful demonstrations since February 2011. People have been voicing their protest at Riyadh's oppressive policies against the country's Shia minority.