The United Nations condemned the "massive loss of civilian lives in western Mosul" in a statement on Tuesday.

UN Human Rights Chief Zeid Raad Al Hussein accused the so-called "Islamic State" (IS) of herding civilians into explosive-rigged buildings in the besieged Iraqi city to "compound devastation."

He said at least 307 civilians had been killed and 273 wounded in western Mosul since February 17 as IS fighters used civilians as human shields and fired on those who fled.

"This is an enemy that ruthlessly exploits civilians to serve its own ends, and clearly has not even the faintest qualm about deliberately placing them in danger," he said in a statement.

"It is vital that the Iraqi Security Forces and their coalition partners avoid this trap," he said, while calling for them to conduct transparent investigations into deadly incidents involving their forces.

Air strike or IS trap?

On March 17, an explosion in the al-Jadida district killed more than 200 people. Investigators were in Mosul on Tuesday to determine whether a coalition air strike or IS explosives caused the blast, a US military commander said.

Iraq's military command blamed militants for rigging the building with explosives to cause civilian casualties, but some witnesses said an air strike hit the building, burying many families under the rubble.

"It is very possible that Daesh (IS) blew up that building to blame it on the coalition in order to cause a delay in the offensive on Mosul and cause a delay in the use of coalition air strikes," US Army chief of staff Mark Milley said.

"It is possible that a coalition air strike did it. We don't know yet. There are investigators on the ground."

The Iraqi Observatory for Human Rights said since the campaign against western Mosul began, there were unconfirmed reports of nearly 700 civilians killed by coalition air strikes or IS action.

Inadequate care

Rights Group Amnesty International on Tuesday said the high civilian death toll suggested that coalition forces in Mosul failed to take adequate precautions to prevent civilian deaths.

"The fact that Iraqi authorities repeatedly advised civilians to remain at home instead of fleeing the area, indicates that coalition forces should have known that these strikes were likely to result in a significant numbers of civilian casualties," said Amnesty's Donatella Rovera, who carried out field investigations in Mosul.

Amnesty's report also cited a second strike on Saturday that it said killed "up to 150 people."

Evidence gathered on the ground in Mosul "points to an alarming pattern of US-led coalition airstrikes which have destroyed whole houses with entire families inside," the report stated.

Rambo mentality

Germany's Greens party leader Anton Hofreiter said on Tuesday that Germany should not take part in the "Rambo mentality" of the coalition forces.

The Bundeswehr supports coalition air raids on IS positions in Iraq and Syria from Turkey with Tornado reconnaissance aircraft and a tanker aircraft.

aw/rc (Reuters, dpa, AP)