China's Foreign Ministry said that the ETIM has released a video online and expressed support for the March 1 attack in Kunming city, capital of Yunnan province in southwest China.
"It has fully exposed the terrorist nature of the ETIM," Foreign Ministry spokesman Hong Lei said at a daily news briefing.
"Terrorism is a common enemy of mankind. Fighting against the ETIM is a key component of the international anti-terrorism war," Hong said.
Police did not identify the ethnicity of the assailant, but it was the latest in a series of attacks pointing to growing unrest in the sprawling region.
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The ETIM, listed by the United Nations Security Council as a terrorist group, claimed responsibility for the Tian'anmen attack in October in which five people were killed and 40 others injured.
Officials believe that the March 1 attack that left 33 people dead and 143 others injured was also carried out by ETIM separatists.