Demonstrators take to the streets after the killing of civil activist Ehab Jawad al-Wazi near his home in Karbala.
Iraqi security forces have arrested senior militia commander Qasim Muslih under the country’s anti-terrorism law, the military said.
Muslih was arrested early on Wednesday and is being questioned by a joint investigative committee about the criminal charges against him, a military statement added, without giving further details.
Two security sources with direct knowledge of the arrest told Reuters news agency that the militia chief was arrested in Baghdad for involvement in several attacks, including recent assaults on Ain al-Assad airbase which hosts American and other international forces.
Muslih is the Anbar province head of the Popular Mobilisation Forces (PMF), a grouping of mostly Shia militias backed by Iran, which the United States regards as the biggest threat to security in the Middle East.
A copy of the arrest warrant issued for Muslih that circulated on social media and was verified by the security sources said he was arrested under the anti-terrorism law, but did not have further information.
The airbase was attacked at least four times this month with rockets and an unmanned aerial surveillance system, in incidents seen by many Iraqis as reflecting US-Iranian tensions.
But a security source told the AFP news agency his arrest was in connection with the killing of two civil society activists in recent weeks.
“At dawn in Baghdad, police intelligence arrested Qasem Muslah, Popular Mobilisation Forces (Hashed) operations chief for Anbar province, who gave the order to kill Ihab al-Wazni on May 9 and another activist Fahim al-Taie in December 2019,” the security source said.
“We initially had clues about the perpetrators of the murders and verification allowed us to identify with certainty the person who was behind these criminal operations,” the source added.
Anti-government campaigner Wazni was shot dead outside his home by men on motorbikes using a gun equipped with a silencer early on May 9 in the holy shrine city of Karbala, sending protest movement supporters onto the streets to demand an end to such bloodshed and official impunity.
Wazni had for many years criticised Iraqi armed groups and Iran’s influence in the country, leading protests in Karbala, where pro-Tehran armed groups hold considerable sway.
Killings, attempted murder and abductions have targeted more than 70 activists since a protest movement erupted against government corruption and incompetence in 2019.
Following the arrest, unidentified gunmen drove vehicles around the fortified Green Zone, which hosts foreign embassies and government buildings, as a show of force, a security source said. The source, who spoke on condition of anonymity, said the show only lasted for half an hour and then they withdrew.
A Reuters reporter who tried to drive through the Green Zone said security forces did not allow him in and he was forced to leave, adding there was a heavy security presence in the area.
Another Reuters reporter said there were dozens of PMF forces who were in control of one of the entrances to the Green Zone and were not allowing anyone in.
The Hashed had quickly issued a statement promising Muslih “would be released in the coming hours”.
Powerful paramilitary groups aligned with Iran in Iraq have launched attacks against US targets in the country.
Most of the incidents have caused no casualties, but they have kept up the pressure on US troops and US allies in the early days of Joe Biden’s presidency.
Iraq’s government under Prime Minister Mustafa al-Kadhimi has sided with the US but has found it hard to bring the groups under control.
Last year, Iraqi security forces raided a stronghold of a powerful Iran-backed militia in Baghdad and arrested more than a dozen members of the group. Shortly after the arrest, unidentified gunmen drove vehicles towards government buildings in the Green Zone demanding the release of the militiamen.
Most of the men were released within hours.