HONG KONG — Police officers in Hong Kong on Sunday fired tear gas and fought with angry demonstrators outside a luxury hotel, another sign of fraying civility in a financial hub roiled by nearly five months of protests.

The protesters began gathering in the afternoon in the same shopping district where a week earlier the police used water cannons with stinging blue dye to clear a peaceful demonstration outside a mosque. The rally on Sunday was billed partly as a show of support for the city’s ethnic minorities.

Riot police officers fired tear gas on the demonstrators less than an hour after the rally began, and there was a heavy police presence in the area well into the night.

The rally on Sunday was unauthorized and came a day after a local court issued a temporary order that bans the harassment of police officers.