Pro-democracy protesters reinforce a barricade in the Mongkok district of Hong Kong on October 13, 2014. (Agence France-Presse)
The United States said on Wednesday it was "deeply concerned" by reports of Hong Kong police beating a handcuffed protester, calling for a "swift, transparent and complete" investigation of the incident.
"We renew our call for the Hong Kong government to show restraint, and for protesters to continue to express their views peacefully," State Department spokeswoman Jen Psaki told reporters.
The plainclothes officers accused of wrongdoing were removed from their posts after the assault, which occurred early on Wednesday when police swooped to clear barricades blocking a road near the Chinese city's government headquarters.
Without calling out China, Psaki hailed Hong Kong's "well-established tradition of respect for the rule of law and internationally recognized fundamental freedoms" and said they were crucial to its success as a global financial hub.
Crowds -- sometimes numbering in the tens of thousands -- have blocked main roads in three districts of the semi-autonomous Chinese city since September 28, protesting at what they call "fake democracy" offered by Beijing.
They are angered at China's insistence that it vet candidates standing for election as Hong Kong's next leader in 2017.