Kenya said on Wednesday it had deported 82 Somalis and rounded up hundreds of others without proper documents, part of a security crackdown launched after repeated attacks claimed by militants from neighboring Somalia.
Police had detained 472 people in the past few days, Interior Cabinet Secretary Joseph Ole Lenku told reporters at a stadium where other people were being screened to establish their identity.
"The process will continue until we do not have illegal aliens and those found to have refugees documents are taken to refugees camps," Lenku said.
Muslim leaders say they have been targeted unfairly by the arrests - and Human Rights Watch has called on Kenya to reconsider plans to move Somali refugees from cities to camps. Kenya says the measures are vital to security.
Islamist militants from Somalia's al-Shabaab group killed at least 67 people in a raid on Nairobi's Westgate mall last year and have threatened more attacks unless Kenya pulls its troops out of Somalia.
Kenya, along with Uganda and Ethiopia, has been contributing to an African Union force fighting the al-Qaida-linked movement. Gunmen shouting in a foreign language killed six worshippers in a church near Kenya's coastal city of Mombasa last month. Kenyan authorities reacted by ordering all Somali refugees living in its urban areas to return to two camps closer to the countries' shared border.
They have also arrested people in Nairobi's Somali-dominated Eastleigh area known as "Little Mogadishu." At the stadium, Mariam Mohammed, 25, said she had been separated from her two children and husband when she was detained in Eastleigh.
A policeman guards suspected Somali illegal migrants arrested at a holding station in Kenya's capital Nairobi, April 7, 2014.
Shedding tears as she waited to have her documents checked, she said, "I am ready to go back to my country since I have suffered enough while in custody."
Lenku defended the exercise, saying it was within the law and detainees were getting food and water. More arrests would take place across the country, he added.
Rights groups and aid agencies were allowed into the stadium on Wednesday for the first time since the screening started over the weekend.
Emmanuel Nyabera, a information officer with the U.N. refugee agency UNHCR, said its officers had found detainees with the proper documentation were being released.