A community centre for African-Caribbean pensioners was evacuated and closed after racist threats were made in a telephone call.
Dorothy Evans, who runs the African Caribbean Care Group centre in Hulme, Manchester, said she was left "shocked" and "appalled" by the threats.
The caller made references to slavery and threatened to "make somebody pay".
Greater Manchester Police said reports of race hate incidents had seen a "slight rise" in the last 24 hours.
The incident in Hulme happened at about 12:30 BST on Wednesday, roughly 24 hours after a US Army veteran was racially abused on a tram in Manchester.
Ms Evans said: "Once the caller was clear about the name of the organisation, he went on to make racist statements about people in the community."
The man used "extremely foul language" and said "somebody would be attacked", she added.
Police were called and staff decided to close the Rolls Crescent centre, and about 40 people were sent home.
"We needed to make our staff and service users aware and evacuated the service immediately" Ms Evans said.
"These are people who are elderly. Some of them are infirm. They were exceptionally upset.
"It's come as a shock. We've never, ever had any problem in our community and now this has happened."
Assistant Chief Constable Rob Potts said: "In the past 24 hours we have seen a slight increase in reports of hate crime, particularly race hate incidents.
"We are continuing to monitor the situation to see whether this is an increasing trend, or if it may be related to calls for people to report hate incidents to police.
"We treat hate crime reports very seriously. It will not be tolerated in our communities and it is important that we stand together."