Human rights bodies on Friday urged authorities in Ethiopia to end arbitrary arrests and detentions of ethnic Tigrayans.
Those detained have included activists and journalists.
In a statement, Amnesty International said police in Addis Ababa have arrested and detained dozens of Tigrayans without due process.
"The arrests appear to be ethnically motivated, with former detainees, witnesses and lawyers describing how police checked identity documents before arresting people and taking them to detention centers," the organisation said.
Police crackdown against Tigrayans in the capital started shortly after the Tigray region's capital, Mekelle, was recaptured on June 28, by the outlawed Tigray People's Liberation Front (TPLF).
The global human rights watchdog urged the Ethiopian government either to charge or release the detained Tigrayans.
It further asked Prime Minister Abiy Ahmed's government to reveal the whereabouts of the unaccounted civilians detained in unknown locations.
“Following the withdrawal of the Ethiopian National Defense Force from parts of Tigray and the announcement of a unilateral cease-fire by the federal government on June 28, for the last two weeks Tigrayans in Addis Ababa have been arbitrarily arrested and detained. Former detainees told us that police stations are filled with people speaking Tigrinya, and that authorities had conducted sweeping mass arrests of Tigrayans,” said Deprose Muchena, Amnesty International’s director for East and Southern Africa.
Amnesty called on the Ethiopian government to "end this wave of arbitrary arrests, and to ensure that all detainees are either promptly charged with internationally recognised crimes and given fair trials, or immediately and unconditionally released."
It added: "The government should also inform families of the whereabouts of the detainees and ensure that they have access to lawyers and families.
"While some people have been released on bail, approximately hundreds of others remain in detention, and their whereabouts unknown" said Amnesty
Meanwhile, Ethiopian Human Rights Commission (EHRC) said it is monitoring reports of arbitrary detention and arrests, closure of businesses and other forms of harassment targeting ethnic Tigrayans in Addis Ababa.
"In Addis Ababa, reports indicate that some suspected detainees including media workers have been transported to locations outside the capital and may face continued harassment" the commission said.
The commission urged the Ethiopian government to free all civilians detained without sufficient legal grounds and denied due process.
It also called on federal and regional authorities to hold accountable law enforcement officials who are responsible for arbitrary arrests, harassment, or those who committed other forms of right violations.
Meanwhile, a Tigrayan victim spoke to Nation.Africa about the latest crackdown.
Mr Hailu Amaha (last name changed for safety reasons) was arrested last Saturday along with 26 others from a bar and restaurant near his home.
"All of a sudden, a group of policemen arrived and ordered us to board a patrol vehicle that was parked outside," he said.
"When some of us started to ask why we are being arrested, they started to beat us," he said.
He added: "They took everyone inside that bar that evening including the owner of the restaurant to jail."
Amaha said police later said that the reason for their arrest was that they were not wearing face mask.
But he says they were targeted on the basis of their identities and still fear getting rearrested again, despite their release after four days in jail.
Addis Ababa and the Federal police have denied the allegations.