Police grabbed people by their collars and pulled them away from a designated mourning area if they tried to enter without carrying flowers.
"Shame on (the officials]. How dare they say the rescue was successful? We feel so sorry for those miserable families, but not for the government," said one witness to the blaze.
China's officials are highly sensitive to any mass gathering that could swing into anger and unrest. Neither China Central Television's nightly newscast nor the front page of the state-run Xinhua News Agency website mentioned the extraordinary gathering.
The fire swept through the 28-storey building last Monday after sparks from welding equipment set nylon construction netting and bamboo scaffolding alight. Some people scrambled down the scaffolding to escape.
The Shanghai government said most of the victims died inside their homes, overcome by smoke, toxic fumes and heat. Another 71 were injured, and an unknown number of people are still unaccounted for.
Anguished family members and others angry over the government's handling of the disaster are demanding answers.
Wang Yinxing, a resident of the building whose wife Wang Hao died in the fire, said that he and other survivors were not at the site yesterday because they were "not in the mood".
"The rescue was not timely or helpful enough," he said. "I don't believe anything the government says."
The seventh day is a traditional day of mourning in China, and the authorities seemed prepared for yesterday's large showing. Quiet crowds filed past the building, which was blocked off by police barricades. Just before the building was a huge pile of flowers, stuffed animals, photographs of victims and offerings of cigarettes.
China's work safety chief has blamed the fire on illegal contracting, dangerous materials and poorly supervised, unqualified workers. The Xinhua new agency said police have arrested 12 suspects, including four welders who were allegedly working without proper qualifications.
"We feel deeply about this," Shanghai's Communist Party chief Yu Zhengsheng told victim's families on Friday, the Beijing Times reported. "We'll do our best to help you overcome your difficulties."
The fire happened not long after the end of the six-month World Expo, which was meant to show off Shanghai's development but came with an element of tension for residents who were often reminded to behave themselves.The city is one of China's best-run, but its public services still lag far behind its often ultramodern infrastructure.
The fire has raised alarm over China's widespread efforts to meet energy efficiency targets by adding insulation to the outside of existing buildings - the project the welders were working on when the fire broke out.
Although the insulation meant for such work is supposed to be treated with fire retardants, it is nonetheless flammable. Many are now questioning if the energy savings are worth the risk.