BAGHDAD (AP) — The top Shiite cleric in Iraq on Saturday called for the release of 18 Turkish workers kidnapped in Baghdad last week, a day after a video released by a shadowy militant group showed the captives and threatened Ankara with the "most violent means" if its demands are not met.

The men, employed by Turkish construction company Nurol Insaat, were snatched up from a construction site in Baghdad's Shiite-dominated Sadr City on Sept. 2. An Iraqi national was kidnapped along with the Turks.

In a statement on his website, Grand Ayatollah Ali al-Sistani said abducting "these innocents who have nothing to do with the events and tragedies in the region is unethical, illegitimate and illegal."

"We call for releasing the captives and stopping these practices," which harm Islam, he added.

The 3-minute video shows the captives in three rows in front of five masked gunmen. Behind them is a blue wall emblazoned with the group's name, "Death Squads." Next to the name are the words "Oh, Hussein" — a reference to a revered Shiite figure who was the Prophet Muhammad's grandson.

At the end of the video, the group demands that Turkey halt the flow of militants into Iraq, lift a "siege" on Syrian Shiite cities and stop the passage of oil from Iraq's northern Kurdish region via Turkey in defiance of Baghdad.

The Iraqi capital has been torn by violence for over a decade now, with roadside bombs, suicide attacks and assassinations occurring almost daily. While kidnapping for ransom has continued, abductions on this scale have been almost unheard of in recent years.