Saudi security forces dispersed crowds of Shiite and Sunni Muslims after scuffles broke out in the city of Medina during the Shiite mourning holiday of Ashoura late on Thursday, Shi'ite sources and a local journalist said.
Top oil exporter Saudi Arabia applies Sunni Islam , and minority Shi'ites say that, while their situation has improved slightly under reforms launched by King Abdullah, they still face many restrictions and discrimination. The government denies these charges.
The Shiite website Rasid.com said a group of Sunnis had attacked several Shiites with stones as they were outside commemorating the Ashoura holiday in Medina, Islam's second holiest city.
A local Shiite resident also confirmed the incident to Reuters. He said it had occurred near the landmark Quba Mosque.
During Ashoura, Shiites mark the slaying in 680 of Prophet Mohammad's grandson Imam Hussein, traditionally in a bloody self-flagellation ritual. But Saudi Arabia's Shiites say they cannot mark the festival at all in public outside some parts of Eastern Province, where they are in the majority.
"Security forces arrived to disperse the crowd," the journalist said, speaking on condition of anonymity. "There has been heavy security presence in Medina since then, with police patrolling streets."
The Saudi current affairs website sabq.org quoted a local police spokesman as saying police had stepped in to end an argument between two groups of young people that involved stone throwing.
"The situation is now totally quiet," spokesman Muhsin al-Radadi was quoted as saying. The website showed a picture of what it said was an ambulance arriving at the scene.
The interior ministry in Riyadh could not be immediately reached for comment.
Officials say Sh'ites make up 10 percent of the Saudi population, though diplomats put it closer to 15 percent. Shiites complain of regular verbal attacks by clerics and difficulties in landing senior government and security jobs, charges the government denies.