STORY: Reuters footage showed crowds of people chanting and holding banners outside the mosque.
Dams above the city burst in a storm a week ago, sending a huge torrent down a seasonal riverbed that runs through the centre of the city of 120,000 people.
Thousands are dead and thousands more missing. Officials using different methodologies have given widely varying figures of the tolls so far; the mayor estimates more than 20,000 people were lost.
The World Health Organization has confirmed 3,922 deaths.