Ethiopia’s prime minister said Saturday his military had taken complete control of the capital of the northern Tigray region, capping a three-week offensive against separatists that forced tens of thousands to flee to Sudan amid reports of mass atrocities. Prime Minister Abiy Ahmed, who won the Nobel Peace Prize in 2019, refused international demands for talks with the Tigray People’s Liberation Front. Members of that group accused Ethiopia’s military of shelling heavily populated areas of the capital Mekelle.