The United States says it has voiced outrage to the Democratic Republic of Congo and Gambia after their leaders’ guards roughed up protesters at an Africa summit in the US.

Jacques Miango, a US-based activist critical of DR Congo President Joseph Kabila, said in an online video that guards beat him and others and stole his laptop as they held a small protest on Wednesday near the leader’s hotel in Washington DC’s tony Georgetown neighbourhood.

“We take the right to freedom of expression very seriously and violence against peaceful protesters is totally unacceptable,” State Department spokeswoman Marie Harf told reporters.

“We communicated our concern to the delegation in the strongest possible terms.”

The US asked DR Congo to waive immunity for the guards so they could face prosecution in the US, but the guards instead left the country on Thursday and were unlikely to face charges, Harf said.

A video of the incident, taken by a passer-by and posted to the video-sharing website YouTube, showed a man who appeared to be a security guard kicking a protester on the ground before storming off.

Harf said the US also asked the delegation of Gambia to waive immunity for a guard after President Yahya Jammeh’s security detail similarly cracked down on protesters outside his hotel.

An exiled Gambian journalist, Fatou Camara, and a protester needed hospital treatment after Jammeh’s guards forcibly dispersed the crowd as the president left the Hay-Adams Hotel near the White House, according to Gainako, a news blog that highlights human rights in the West African country.

Camara described the incident on Twitter as “an attack on democracy and rule of law”, saying: “God save Gambia!”

Fifty African leaders visited the US capital from Monday to Wednesday for a first-of-a-kind summit, which President Barack Obama hoped would promote good governance as well as trade deals.

Telephone calls late on Friday to the DR Congo and Gambian embassies went unanswered.