Although youth gang wars affect all of Indonesia, Yogyakarta, a city of 400,000 inhabitants on the island of Java, has become the epicentre of a worrying new phenomenon. There, teenage boys clash in the streets at night. They travel on motorbike, armed with truncheons or rusty swords. Their victims are rival gang members, but sometimes also innocent passersby. Known as the Klitih, these gangs are spreading terror among the local population, as our regional correspondents report.