Survivors of Hurricane Matthew put on their Sunday finest and picked their way through downed power lines to sing praise and pray in ruined churches, while desperation grew in other parts of devastated Haiti and international rescue efforts began ramping up.

Haitian authorities were still unsure of the extent of the disaster, with some communities still cut off. But tens of thousands of homes were obliterated and the dead number at least a thousand.

Guillaume Silvera, a senior official with the Civil Protection Agency in the storm-blasted Grand-Anse Department, which includes Jeremie, said at least 522 deaths were confirmed there alone — not including people in several remote communities still cut off by collapsed roads and bridges.