Millions of Iranians travel to the Iraqi city of Kerbala every year for the ritual of Arbaeen, which marks the end of a 40-day mourning period for the grandson of the Prophet Mohammad, Imam Hussein.
Streets were mostly empty of ordinary people as gunmen cruised in pickup trucks carrying machine guns and brandishing grenade launchers.
Sixty protesters were injured in clashes with security forces. Three days earlier a mass protest outside parliament by Sadr supporters ended only after Sadr tweeted a request to them to disperse.
Officials said the attacker was a 21-year-old ethnic Uzbek from Afghanistan with radical Sunni views.
Iraq is delaying the presidential race due to many lawmakers boycotting the vote, prolonging a battle over the presidency and a new government being fought largely between Sadr and the pro-Iran camp.
When it comes Afghanistan, Iran's policy is complex.
Hezbollah Secretary-General Hassan Nasrallah condemned the Druze who stopped and filmed the operatives loading rockets towards Israel.
The report states that the axis aims to develop "an active civilian and military integrated infrastructure," as a possible terror base on European soil
In 2014, members of the Sunni Muslim jihadist group opened fire on Shi'ites who were celebrating Ahura, killing eight.
"The roots of our problems are the Zionist regime and American imperialism," Iranian president Hassan Rouhani declared during a military ceremony.