People arrested during ethnic tensions in China's Xinjiang region have been warned that they may be executed.
Li Zhi, the Communist party chief for the city of Urumqi, said "to those who committed crimes with cruel means, we will execute them".
The warning came as protests appeared to calm after at least 156 people were killed in clashes that erupted on Sunday.
Hu Jintao, China's president, left the G8 summit in Italy to return to Beijing early as an indication of how seriously the country is taking the conflict between ethnic Uighurs and Han Chinese.
After a night-time curfew was declared on Tuesday, the Chinese authorities said they had restored order as army helicopters circled Urumqi, the regional capital, and thousands of soldiers and riot police filled the city.
Melissa Chan, Al Jazeera's correspondent in Urumqi, said: "It looks like what the soldiers are doing has been effective, but the question is what will happen next because at some point they will need to withdraw."
Referring to the execution warning in Urumqi, correspondent Steve Chao in Beijing, said: "It's really not surprising if you look at the way the government has dealt with such protests in the past.
"We've seen for example in Tibet, after the unrest of last year, where we saw many people executed as a result of their actions so we're likely to see much more of that.
"The government often takes a very hard line against any voices who really oppose the government or in this case actually kill people on the ground in Xinjiang province."
Makeshift weapons
Despite the massive show of force by Chinese troops that appeared to have brought some calm, mobs wielding makeshift weapons continued to roam the city on Wednesday.
A day earlier, thousands of Han Chinese had rampaged through Urumqi seeking revenge against the Uighurs who they say started deadly riots on Sunday in which most of the victims died.
Groups of Uighurs also took to the streets and government forces fired tear gas at the crowds before ordering the curfew in an effort to maintain control of the city.
The authorities blamed the Uighurs for Sunday's unrest that also left more than 1,000 people injured.
However, Chan reported: "The government ... said in a press conference that if it had not been for the Hu Chinese escalating things, it wouldn't have been so bad, it just would have been one bad riot in one night."
Uighur complaints
Uighur groups say repressive policies by China 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.
The Turkic-speaking Uighurs have long complained of repression and discrimination under Chinese rule, but Beijing insists it has brought prosperity.
On Wednesday, Recep Tayyip Erdogan, Turkey's prime minister, called for an end to the "savagery".
Erdogan said: "Our expectation is for these incidents that have reached the level of savagery to be rapidly stopped."
The prime minister and Ahmet Davutoglu, Turkey's foreign minister, made separate calls to China to bring "those responsible to account" in a transparent manner.
"We are following the events with great concern, worry and sadness," Erdogan said
Industrial dispute
According to Chinese state media, Sunday's clashes erupted after a demonstration against the government's handling of an industrial dispute turned violent.
Beijing singled 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.