By Stephanie Nebehay GENEVA (Reuters) - The United Nations' top human rights official urged Turkey on Monday to investigate the shooting of unarmed people 10 days ago in its largely Kurdish southeast and said any members of the security forces committing rights abuses should be prosecuted. Southeastern Turkey has seen its worst violence in two decades since a 2-1/2-year ceasefire with militants of the Kurdistan Workers' Party (PKK) collapsed last July, reviving a conflict in which 40,000 people have been killed since 1984. U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein was referring to an incident on Jan. 20, in which 10 people were wounded in the town of Cizre when their group, including two opposition politicians, came under fire while rescuing people hurt in earlier clashes.