The UN human rights chief on Friday condemned the Saudi-led coalition's air strike that killed more than 100 people at a Yemen market this week, saying it was "responsible for twice as many civilian casualties as all other forces put together".

"These awful incidents continue to occur with unacceptable regularity. In addition, despite public promises to investigate such incidents, we have yet to see progress in any such investigations," UN human rights chief Zeid Ra'ad Al Hussein said in a statement.

"We are possibly looking at the commission of international crimes by members of the Coalition," Zeid said.

His staff who visited the site of Tuesday's deadly strike and interviewed witnesses "found no evidence of any armed confrontation or significant military objects in the area at the time of the attack".