"We can see from this that Xinjiang is in a period of turmoil, and such incidents could happen again at any time. This is the trend and it's directly related to Beijing's policies."
Unrest in Xinjiang has caused the deaths of more than 100 people in the past year, prompting a tougher stance against Turkic-language speaking Uighurs, many of whom resent government controls on their culture and religion.
Urumqi was the scene of deadly ethnic riots in 2009, with nearly 200 people killed when Uighurs clashed with members of the majority ethnic Han Chinese community. It has been relatively calm since.
Many Chinese took to the Weibo microblogging service to express anger and defiance at the station attack, including Hu Xijin, editor of the influential tabloid the Global Times, who wrote: "We will never be cowed by a handful of bad people."
China's nervousness about militancy, especially Islamic militancy, has grown since a car burst into flames on the edge of Beijing's Tiananmen Square in October, and 29 people were stabbed to death last month in the southwestern city of Kunming.
The government blamed Xinjiang militants for both incidents.
During his visit, Xinhua quoted Xi as saying: "The long-term stability of Xinjiang is vital to the whole country's reform, development and stability; to the country's unity, ethnic harmony and national security as well as to the great revival of the Chinese nation."
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Uighurs have traditionally followed a moderate form of Islam but many have begun adopting practices more commonly seen in Saudi Arabia or Afghanistan, such as full-face veils for women, as China has intensified a security crackdown in recent years.
China reacted to the 2009 riots by pumping money into less-developed southern Xinjiang, in an implicit recognition of the economic causes of the unrest. But it has taken a much harsher line of late, especially towards dissenters.
The government detained Ilham Tohti, a Beijing economics professor who has championed Uighur rights, in January and subsequently charged him with separatism.
Advocates for Tohti say he has challenged the government's version of several incidents involving Uighurs, including the car fire on the edge of Tiananmen Square.