Opposition activists said hundreds were killed in a stampede allegedly provoked by security forces at the Irreecha festival in 2016.
"I think Boris Johnson's response to this situation is bizarre and inexplicable," a senior legal official tells Newsweek.
Police arrested Merera Gudina for "communicating with a banned terrorist organization."
Ethiopia's prime minister has reshuffled his cabinet, but it's unlikely to quell widespread anger.
Tamiru Demisse followed Olympic counterpart Feyisa Lilesa in making anti-government gesture.
Lilesa protested in solidarity with Ethiopia's Oromo community after winning silver in Rio.
Israel's only Ethiopian parliamentarian is upset Netanyahu did not meet with Ethiopian Jews.
More than 100 children were abducted from Ethiopia's Gambella region earlier this month.
Hailemariam Desalegn blamed the violent protests on "anti-peace forces."
Plans to expand Ethiopia's capital have been dropped, but protesters are still being killed, HRW says.