The altar of a Catholic church in the Andersonstown Rd area of West Belfast was smeared with excrement after a break-in last night.
Pews, statues and other items in St Agnes' church were damaged in the incident.
A funeral due to take place at the church this morning had to be moved to nearby St Michaels.
The coffin of a local woman was lying inside the church as it was being burgled.
Sinn Féin councillor Mr Paul Maskey said members of the family were deeply shocked by the incident.
He described the vandals as 'mindless thugs' who had caused unnecessary pain.
'This is a very upsetting time for the family. It's bad enough burying a mother, never mind coming to a chapel on the morning to find out that someone has broken in and done a bit of damage to that chapel,' he added.