China has often blamed ETIM - the East Turkestan Islamic Movement - or people inspired by ETIM for violent incidents both in Xinjiang and beyond the region's borders.
ETIM is said to want to establish an independent East Turkestan in China. The US State Department in 2006 said ETIM is "the most militant of the ethnic Uighur separatist groups".
The scope of ETIM's activities remains unclear with some questioning the group's capacity to organise serious acts of extremism.
ETIM has not said it was behind any of the attacks. Chinese authorities said the Turkestan Islamic Party - which it says is synonymous with ETIM - released a video backing the Kunming attack, however.
With the recent apparent escalation in Xinjiang-related violence, the question of who and what is driving it is likely to attract greater scrutiny.