The violence was "pre-meditated and organised," he is reported to have said.
Uighur groups in the US deny this. They say they are being blamed as a way of distracting attention from the real cause of the Uighurs' discontent, the discrimination they face and the oppression they are subjected to by the Chinese authorities.
It is not the first time the Chinese have suggested this kind of violence is the work of "separatists".
They made similar claims after riots in the Tibetan capital Lhasa last year.
The streets of Urumqi, the capital of Xinjiang, are reported to be quiet although eyewitnesses say there is a heavy security presence.
It is also reported to be impossible to access the internet in that part of China at the moment.
Throughout the morning in China, the official news agency Xinhua offered several updates, revising upwards the estimate of the number killed and injured.
Much of the information came from a news conference in the regional capital given by local officials.
A serious outbreak of ethnic violence like this is, of course, a concern for the authorities.
One of the sparks was said to have been an incident last month in southern China in which two Uighurs were killed during a clash between workers from the Uighur and Han communities.
Xinjiang is, however, a remote part of the country, some 3,000 km ( 1875 miles) from Beijing, so the violence there is unlikely to have much of an impact elsewhere in the country unless there is a sense that in Urumqi the authorities are losing control.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.