Riot police are out in force in Urumqi in a bid to contain a fresh outburst of ethnic violence in the Chinese city.Thousands of Han Chinese armed with iron bars and machetes took to the streets seeking Muslim Uighur targets after Sunday’s bloodshed in which 156 people were killed. It took tear gas and a curfew to restore a degree of calm. Earlier, Uighur had also been on the streets demanding the release of family members they say were arbitrarily detained by police at the weekend. The Xinjiang province has long been a hotbed of ethnic tension and the UN is urging restraint. Rupert Colville, spokesman for the UN High Commissioner for Human Rights, said: “The high commissioner called for a transparent, independent investigation into the cause of the rioting and the reasons why it escalated to the point of causing injuries or loss of life to over a thousand people.” Sunday’s riots were sparked by a protest about the government’s handling of a clash between Han Chinese and Uighur factory workers in southern China in which two Uighur died. The unrest reached levels of violence never before seen in the region.