BAGHDAD, May 26 (Xinhua) -- Iraqi Prime Minister Mustafa al-Kadhimi on Wednesday denounced some armed militia for approaching the heavily fortified Green Zone in central Baghdad, saying their move violates the country's constitution, according to a statement issued by the Iraqi Joint Operation Command (JOC).

The appearance of a group of paramilitary soldiers near the Green Zone sparked a state of emergency as security forces deployed surrounding the zone and blocked all its entrances, a police source told Xinhua on condition of anonymity.

The tension came after the Iraqi government arrested earlier in the day Qasim Mahmoud Karim Muslih, a commander of Hashd Shaabi forces, over the charges of terrorism.

"We have directed an immediate investigation into these movements (of armed groups), according to the law," said al-Kadhimi, who is also commander-in-chief of the Iraqi forces.

Al-Kadhimi said an investigative committee composed of the JOC, the Interior Intelligence, Military Intelligence, National Security, and the Hashd Shaabi Security Service was formed to investigate the accusations against Muslih, noting Muslih is being held by the JOC until the investigation is completed, according to the statement.

At dawn, a security force arrested Muslih from his home in Doura district in southern Baghdad. The arrest triggered criticisms and dissatisfactions from some influential Shitte military groups.

Qais al-Khazali, head of the Asa'ib Ahl al-Haq Movement, demanded that Muslih be handed over to the Hashd Shaabi Security Service, considering the arrest "as an attempt to confuse the security situation."

According to local media reports, leading Shiite politicians are holding meetings with the government and Hashd Shaabi leaders to ease the tension in the Iraqi capital. Enditem