"Because of the unprecedented scale and the severity of the situation in Xinjiang," he told Al Jazeera, Hu had taken the "unprecedented measure of leaving the G8 meeting before it starts and coming back to China to exercise his leadership role in calming down the situation in Xinjiang".
Al Jazeera's Melissa Chan, reporting from Urumqi, said tensions were rising again after a relatively calm Wednesday morning following a curfew overnight.
Ethnic Han Chinese were taking to the streets, our correspondent said, carrying sticks and trying to enter Uighur neighbourhoods dotted around the predominantly Han city despite riot police blocking off main streets and armoured personnel carriers conducting patrols.
On Tuesday, thousands of Han Chinese had rampaged through the city seeking revenge against ethnic Uighurs who they say started Sunday's deadly riots.
Groups of Uighurs also took to the streets and government forces fired tear gas at the crowds and ordered the imposition of a curfew in an effort to maintain control of the city.
According to Chinese authorities at least 156 people died in Sunday's riot which broke out after a street protest by ethnic Uighurs turned violent.
The riot was some of the deadliest ethnic unrest seen in the country for decades.
Chinese police are reported to have arrested more than 1,400 people in a crackdown that Wang Lequan, the head of the Chinese Communist party in Xinjiang, said was intended to quell the unrest, although he warned "this struggle ... against separatism ... is far from over".
|Uighurs say Chinese repression and mass Han migration have stoked tensions [Reuters]
Commenting on the government's handling of the crisis, Victor Gao, who worked as translator for the late Chinese leader Deng Xiaoping, said the government needed to be "very fair and very effective" in tackling the situation.
"It is easy to draw the line along ethnic groups, however it is a temptation that we need to resist," he said.
"I think it's better to focus on the criminal activities regardless of which ethnic group they are, whether they are Uighurs or Han Chinese."
Uighur groups say China's repressive policies combined with years of mass migration to Xinjiang by Han Chinese, China's largest ethnic group, have stoked ethnic tensions and sown the seeds for violence.
Asked if Beijing needed to reconsider its "go west" policy encouraging the Han migration, Gao said China "should not deviate from the overall situation regardless of what's happening in Urumqi right now".
"It is a severe incident, it's a great embarrassment for us Chinese, but I think we need to continue because I think without stability, improvements of the living standards of the people in Xinjiang, including the Uighurs, will be out of the question."
According to Chinese state media, Sunday's clashes erupted after a demonstration against the government's handling of an industrial dispute turned violent.
Beijing blames Uighur exiles for stoking the unrest, singling out Rebiya Kadeer, a Uighur businesswoman who was jailed for years in China before being released into exile in the US where she now heads the World Uighur Congress, for "masterminding" the unrest.
But Kadeer, a 62-year-old mother of 11, has rejected the accusations, saying from Washington DC that they were "completely false".
Activists say the clashes started when armed police moved in to break up a peaceful demonstration called after two Uighur workers at a toy factory in southern China were killed in a clash with Han Chinese staff late last month.
Kadeer said the protests in Urumqi started peacefully.
"They were not violent as the Chinese government has accused. They were not rioters or separatists," she said.
She did, however, condemn "the violent actions of some of the Uighur demonstrators", saying she supported only peaceful protests.