The United Nations' human rights agency says it has received reports that Yemeni troops have killed more than 50 anti-government protesters in the city of Taiz since Sunday. Human rights chief Navi Pillay on Tuesday condemned the government's intensified use of force on protesters, calling its acts reprehensible and urged the government to make sure the human rights of its citizens are protected. She also criticized the security forces for occupying a hospital in Taiz and destroying a field clinic near the protesters' camp. Pillay said medical staff and facilities should never be targeted by government forces. Meanwhile, fighting continues in Taiz, and it restarted on Tuesday in the capital, Sana'a, indicating the breakdown of a truce between tribal leaders and forces loyal to President Ali Abdullah Saleh. Yemeni forces killed more than 20 opposition demonstrators in Taiz.