GENEVA, July 24 — US police and security forces must not use disproportionate force against protesters and journalists in US cities including Portland or detain them unlawfully, the United Nations human rights office said today.

"There have been reports that peaceful protesters have been detained by unidentified police officers and that is a worry because it may place those detained outside the protection of the law and may give rise to arbitrary detention and other human rights violations,” Liz Throssell, UN human rights spokeswoman, told a Geneva news briefing.

"The authorities should ensure that federal and local security forces deployed are properly and clearly identified and would use force only when necessary, proportionately and in accordance with international standards,” she said.

The US Justice Department said yesterday it would investigate the use of force by federal agents against protesters in Portland after another night of unrest in which Mayor Ted Wheeler was tear-gassed. — Reuters