A statement from Prime Minister Sheikh Hasina, mourning the deaths and thanking the rescuers, was read out ahead of the prayers.
Signs of dissension are also emerging among clothing brands and retailers who as a group have usually sought to distance themselves from industry disasters.
There were about 3,000 people inside the complex when it collapsed. About 2,500 people have been rescued, many injured, but many remain unaccounted for.
Spokeswoman Julija Hunter said the company is still working out the details, but plans to deliver support.
Officials said the Rana Plaza, on the outskirts of the capital, Dhaka, had been built illegally without the correct permits.
A fire official said at least two dozen people were still expected to be alive under the concrete garbage.
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