'The Shenzhen special economic zone created a miracle in the world's history of industrialisation, urbanisation and modernisation and has contributed significantly to China's opening up and reform,' Hu said.

'The central government will, as always, support the brave experiments of the special economic zones as well as in their role of testing and carrying out reforms ahead of other regions,' he added.

Hu pledged more central endorsement of Shenzhen's future economic reforms, and his remark focused on the city's future economic development rather than political reforms, as Premier Wen Jiabao had stressed in his visit last month.

Commentators said the one-hour ceremony was more an observance of the special economic zone's achievements. Three Shenzhen-based mainland company executives and Hong Kong's richest man, Li Ka-shing, gave speeches about the tremendous changes in the economic arena. That suggested authorities do not want to commit to future political reforms, even though Wen told party cadres that they must continue to liberate their thinking and make bold moves to achieve democracy.

Hong Kong Chief Executive Donald Tsang Yam-kuen, Macau Chief Executive Fernando Chui-sai and Guangdong party secretary Wang Yang attended the ceremony.

The millions of migrant workers who built the booming manufacturing heartland were not represented; instead, carefully selected spectators with clean criminal records joined government employees, military personnel and medical workers sitting quietly in a stadium on the outskirts three hours before Hu's arrival, with no smiles on their fatigued faces. They were required to practise standing up to applaud several hours before the ceremony began.

The stadium was newly built in a university town in Xili district, which is only two kilometres from the villa for top leaders where Hu stayed during his two-day visit.

All roads leading to the remote venue were blocked by police from early morning, and reporters were restricted from the location and seeing the schedule until the last minute.

Mobile phones, laptops, handbags, cigarette-lighters and water were all banned. Spectators weren't allowed to take pictures, walk around or stand up without permission. Several thousand security guards, policemen and soldiers stood guard at every entrance and stairway, closely watching everyone.

In the city, authorities had tightened control over petitioners to prevent them from launching protests during Hu's visit.

Residents of nearly 200 low-income households who had expected to benefit from the government-subsidised housing project but found it had been shoddily constructed protested outside the city's Intermediate People's Court yesterday morning even though they had been ordered not to do so. 'We've been under a lot of pressure and have been harassed by many [government] departments since last week,' said a Shenzhen resident who said he had frequently protested about shabby construction. 'We were asked by the community government to take a free tour to Shanghai between Saturday and Monday,' said the petitioner, who would not give his name for fear of reprisals. 'Most of us refused to leave the city since we heard Hu Jintao would come and hoped he could know about the injustice we are suffering.'

No residents had been detained yesterday.

China's first four special economic zones - Shenzhen, Zhuhai and Shantou in Guangdong and Xiamen , Fujian, were established in 1980. The official celebrations were postponed for 12 days after Hu decided to stay in Beijing in the wake of the Manila bus hostage tragedy.