The January U.S. drone strike in Iraq that killed top Iranian general Qassem Soleimani and nine other people represented a violation of international law, a U.N. human rights investigator said on Monday.

The United States has failed to provide sufficient evidence of an ongoing or imminent attack against its interests to justify the strike on Soleimani’s convoy as it left Baghdad airport, said Agnes Callamard, U.N. special rapporteur on extrajudicial, summary or arbitrary executions.

The attack violated the U.N. Charter, Callamard wrote in a report calling for accountability for targeted killings by armed drones and for greater regulation of the weapons.

“The world is at a critical time, and possible tipping point, when it comes to the use of drones. … The Security Council is missing in action; the international community, willingly or not, stands largely silent,” Callamard, an independent investigator, told Reuters.

Callamard is due on Thursday to present her findings to the Human Rights Council, giving member states a chance to debate what action to pursue. The United States is not a member of the forum, having quit two years ago.

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