China said on Thursday that it would mount a sustained campaign to restore security in Xinjiang, combining mass mobilisation of communist party units in the region with a pledge to deal ruthlessly with the “criminals” behind the week’s violence.

Hu Jintao, the president and communist party head, convened an emergency meeting of the leadership, the nine-member inner-circle of the Politburo, hours after arriving home on Wednesday from his truncated G8 trip to Italy.

The management of the crisis is a high-profile test for Mr Hu, who must satisfy the demands of hardliners within the party for a tough response, with an eye on the sensitivities of Muslim countries offshore.

China has blamed Sunday’s violence in Urumqi, which left 156 people dead and more than a thousand injured, on Xinjiang’s indigenous Muslim population, the Uighurs.

The statement issued by the Politburo late on Thursday reiterated the claim made by Beijing within hours of the riot, that it had been “meticulously planned and organised” by anti-China forces offshore.

“The planners and organisers as well as serious violent criminals involved in the incident must be severely punished in accordance with the law,” the statement said.

Turkey, echoing a call made in editorials in many countries in the Muslim world, including some in Pakistan, a long-time Beijing ally, called for China to show restraint in the handling of the Uighurs

“Our expectation is for these incidents that have reached the level of savagery to be rapidly stopped,’ said Recep Tayyip Erdogan, Turkey's prime minister, according to the Associated Press.

China on Thursday rejected out of hand a call by Turkey to have the issue discussed by the UN Security Council, of which Ankara is a member, saying that Xinjiang was an internal issue.

Commercial life gradually resumed on Thursday in Urumqi, the Xinjiang capital, under a blanket of security.

Banks, restaurants, department stores and other shops in the main commercial areas in the city centre reopened, and the roads filled with buses, taxis and private cars again.

The security presence remained heavy, with convoys of army trucks circling the main roads and armed police and soldiers patrolling the walkways and checking people’s identification at the entrance of residential compounds and alleys.

Most of the city’s Han Chinese population returned to work. However, many members of ethnic minorities including Uighurs, Xinjiang’s predominant ethnic group, Hui, and Kazakhs, stayed at home out of fear of reprisal attacks.

The Grand Bazaar, the traditional trading area, remained closed. Soldiers camped in the courtyard next to the mosque and guarded the Bazaar’s gate. Tanks and army trucks were parked in front of the gate.

The government continued blanketing the city with propaganda leaflets and broadcasts, calling on citizens from all ethnic groups to show mutual tolerance and support.

“Stability means happiness, chaos means disaster,” said one slogan glued to walls on red and blue strips of paper.

The Politburo’s call for the party’s grassroots to be mobilised, in the form of party cells in neighbourhoods, enterprises and schools underlines how traditional China’s response to the violence so far has been.

The Politburo acknowledged no need to review policy towards China’s minorities, but instead to “strengthen ideological and political work”.